Influence of bacterial toxins on the GTPase activity of transducin from bovine retinal rod outer segments

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rybin, V.O.; Gureeva, A.A.

1986-05-10

The action of cholera toxin, capable of ADP-ribosylation of the activator N/sub s/ protein, and pertussis toxin, capable of ADP-ribosylation of the inhibitor N/sub i/ protein of the adenylate cyclase complex, on transducin, the GTP-binding protein of the rod outer segments of the retina, was investigated. It was shown that under the action of pertussis and cholera toxins, the GTPase activity of transducin is inhibited. Pertussin toxin inhibits the GTPase of native retinal rod outer segments by 30-40%, while GTPase of homogeneous transducin produces a 70-80% inhibition. The action of toxins on transducin depends on the presence and nature ofmore » the guanylic nucleotide with which incubation is performed. On the basis of the data obtained it is suggested that pertussis toxin interacts with pretransducin and with the transducin-GDP complex, while cholera toxin ADP-ribosylates the transducin-GTP complex and does not act on transducin lacking GTP.« less

Molecular determinants of Guanylate Cyclase Activating Protein subcellular distribution in photoreceptor cells of the retina.

PubMed

López-Begines, Santiago; Plana-Bonamaisó, Anna; Méndez, Ana

2018-02-13

Retinal guanylate cyclase (RetGC) and guanylate cyclase activating proteins (GCAPs) play an important role during the light response in photoreceptor cells. Mutations in these proteins are linked to distinct forms of blindness. RetGC and GCAPs exert their role at the ciliary outer segment where phototransduction takes place. We investigated the mechanisms governing GCAP1 and GCAP2 distribution to rod outer segments by expressing selected GCAP1 and GCAP2 mutants as transient transgenes in the rods of GCAP1/2 double knockout mice. We show that precluding GCAP1 direct binding to RetGC (K23D/GCAP1) prevented its distribution to rod outer segments, while preventing GCAP1 activation of RetGC post-binding (W94A/GCAP1) did not. We infer that GCAP1 translocation to the outer segment strongly depends on GCAP1 binding affinity for RetGC, which points to GCAP1 requirement to bind to RetGC to be transported. We gain further insight into the distinctive regulatory steps of GCAP2 distribution, by showing that a phosphomimic at position 201 is sufficient to retain GCAP2 at proximal compartments; and that the bovine equivalent to blindness-causative mutation G157R/GCAP2 results in enhanced phosphorylation in vitro and significant retention at the inner segment in vivo, as likely contributing factors to the pathophysiology.

Prominin-1 Localizes to the Open Rims of Outer Segment Lamellae in Xenopus laevis Rod and Cone Photoreceptors

PubMed Central

Han, Zhou; Anderson, David W.

2012-01-01

Purpose. Prominin-1 expresses in rod and cone photoreceptors. Mutations in the prominin-1 gene cause retinal degeneration in humans. In this study, the authors investigated the expression and subcellular localization of xlProminin-1 protein, the Xenopus laevis ortholog of prominin-1, in rod and cone photoreceptors of this frog. Methods. Antibodies specific for xlProminin-1 were generated. Immunoblotting was used to study the expression and posttranslational processing of xlProminin-1 protein. Immunocytochemical light and electron microscopy and transgenesis were used to study the subcellular distribution of xlProminin-1. Results. xlProminin-1 is expressed and is subject to posttranslational proteolytic processing in the retina, brain, and kidney. xlProminin-1 is differently expressed and localized in outer segments of rod and cone photoreceptors of X. laevis. Antibodies specific for the N or C termini of xlProminin-1 labeled the open rims of lamellae of cone outer segments (COS) and the open lamellae at the base of rod outer segments (ROS). By contrast, anti–peripherin-2/rds antibody, Xper5A11, labeled the closed rims of cone lamellae adjacent to the ciliary axoneme and the rims of the closed ROS disks. The extent of labeling of the basal ROS by anti–xlProminin-1 antibodies varied with the light cycle in this frog. The entire ROS was also faintly labeled by both antibodies, a result that contrasts with the current notion that prominin-1 localizes only to the basal ROS. Conclusions. These findings suggest that xlProminin-1 may serve as an anti–fusogenic factor in the regulation of disk morphogenesis and may help to maintain the open lamellar structure of basal ROS and COS disks in X. laevis photoreceptors. PMID:22076989

Molecular basis for photoreceptor outer segment architecture

PubMed Central

Goldberg, Andrew F. X.; Moritz, Orson L.; Williams, David S.

2016-01-01

To serve vision, vertebrate rod and cone photoreceptors must detect photons, convert the light stimuli into cellular signals, and then convey the encoded information to downstream neurons. Rods and cones are sensory neurons that each rely on specialized ciliary organelles to detect light. These organelles, called outer segments, possess elaborate architectures that include many hundreds of light-sensitive membranous disks arrayed one atop another in precise register. These stacked disks capture light and initiate the chain of molecular and cellular events that underlie normal vision. Outer segment organization is challenged by an inherently dynamic nature; these organelles are subject to a renewal process that replaces a significant fraction of their disks (up to ~10%) on a daily basis. In addition, a broad range of environmental and genetic insults can disrupt outer segment morphology to impair photoreceptor function and viability. In this chapter, we survey the major progress that has been made for understanding the molecular basis of outer segment architecture. We also discuss key aspects of organelle lipid and protein composition, and highlight distributions, interactions, and potential structural functions of key OS-resident molecules, including: kinesin-2, actin, RP1, prominin-1, protocadherin 21, peripherin-2/rds, rom-1, glutamic acid-rich proteins, and rhodopsin. Finally, we identify key knowledge gaps and challenges that remain for understanding how normal outer segment architecture is established and maintained. PMID:27260426

Comparative investigation of stimulus-evoked rod outer segment movement and retinal electrophysiological activity

NASA Astrophysics Data System (ADS)

Lu, Yiming; Wang, Benquan; Yao, Xincheng

2017-02-01

Transient retinal phototropism (TRP) has been observed in rod photoreceptors activated by oblique visible light flashes. Time-lapse confocal microscopy and optical coherence tomography (OCT) revealed rod outer segment (ROS) movements as the physical source of TRP. However, the physiological source of TRP is still not well understood. In this study, concurrent TRP and electroretinogram (ERG) measurements disclosed a remarkably earlier onset time of the ROS movements (<=10 ms) than that ( 38 ms) of the ERG a-wave. Furthermore, low sodium treatment reversibly blocked the photoreceptor ERG a-wave, which is known to reflect hyperpolarization of retinal photoreceptors, but preserved the TRP associated rod OS movements well. Our experimental results and theoretical analysis suggested that the physiological source of TRP might be attributed to early stages of phototransduction, before the hyperpolarization of retinal photoreceptors.

Inhibition or Stimulation of Autophagy Affects Early Formation of Lipofuscin-Like Autofluorescence in the Retinal Pigment Epithelium Cell

PubMed Central

Lei, Lei; Tzekov, Radouil; Li, Huapeng; McDowell, J. Hugh; Gao, Guangping; Smith, W. Clay; Tang, Shibo; Kaushal, Shalesh

2017-01-01

The accumulation of lipofuscin in the retinal pigment epithelium (RPE) is dependent on the effectiveness of photoreceptor outer segment material degradation. This study explored the role of autophagy in the fate of RPE lipofuscin degradation. After seven days of feeding with either native or modified rod outer segments, ARPE-19 cells were treated with enhancers or inhibitors of autophagy and the autofluorescence was detected by fluorescence-activated cell sorting. Supplementation with different types of rod outer segments increased lipofuscin-like autofluorescence (LLAF) after the inhibition of autophagy, while the induction of autophagy (e.g., application of rapamycin) decreased LLAF. The effects of autophagy induction were further confirmed by Western blotting, which showed the conversion of LC3-I to LC3-II, and by immunofluorescence microscopy, which detected the lysosomal activity of the autophagy inducers. We also monitored LLAF after the application of several autophagy inhibitors by RNA-interference and confocal microscopy. The results showed that, in general, the inhibition of the autophagy-related proteins resulted in an increase in LLAF when cells were fed with rod outer segments, which further confirms the effect of autophagy in the fate of RPE lipofuscin degradation. These results emphasize the complex role of autophagy in modulating RPE autofluorescence and confirm the possibility of the pharmacological clearance of RPE lipofuscin by small molecules. PMID:28353645

High temperature control rod assembly

DOEpatents

Vollman, Russell E.

1991-01-01

A high temperature nuclear control rod assembly comprises a plurality of substantially cylindrical segments flexibly joined together in succession by ball joints. The segments are made of a high temperature graphite or carbon-carbon composite. The segment includes a hollow cylindrical sleeve which has an opening for receiving neutron-absorbing material in the form of pellets or compacted rings. The sleeve has a threaded sleeve bore and outer threaded surface. A cylindrical support post has a threaded shaft at one end which is threadably engaged with the sleeve bore to rigidly couple the support post to the sleeve. The other end of the post is formed with a ball portion. A hollow cylindrical collar has an inner threaded surface engageable with the outer threaded surface of the sleeve to rigidly couple the collar to the sleeve. the collar also has a socket portion which cooperates with the ball portion to flexibly connect segments together to form a ball and socket-type joint. In another embodiment, the segment comprises a support member which has a threaded shaft portion and a ball surface portion. The threaded shaft portion is engageable with an inner threaded surface of a ring for rigidly coupling the support member to the ring. The ring in turn has an outer surface at one end which is threadably engageably with a hollow cylindrical sleeve. The other end of the sleeve is formed with a socket portion for engagement with a ball portion of the support member. In yet another embodiment, a secondary rod is slidably inserted in a hollow channel through the center of the segment to provide additional strength. A method for controlling a nuclear reactor utilizing the control rod assembly is also included.

Light-dependent translocation of arrestin in rod photoreceptors is signaled through a phospholipase C cascade and requires ATP.

PubMed

Orisme, Wilda; Li, Jian; Goldmann, Tobias; Bolch, Susan; Wolfrum, Uwe; Smith, W Clay

2010-03-01

Partitioning of cellular components is a critical mechanism by which cells can regulate their activity. In rod photoreceptors, light induces a large-scale translocation of arrestin from the inner segments to the outer segments. The purpose of this project is to elucidate the signaling pathway necessary to initiate arrestin translocation to the outer segments and the mechanism for arrestin translocation. Mouse retinal organotypic cultures and eyes from transgenic Xenopus tadpoles expressing a fusion of GFP and rod arrestin were treated with both activators and inhibitors of proteins in the phosphoinositide pathway. Confocal microscopy was used to image the effects of the pharmacological agents on arrestin translocation in rod photoreceptors. Retinas were also depleted of ATP using potassium cyanide to assess the requirement for ATP in arrestin translocation. In this study, we demonstrate that components of the G-protein-linked phospholipase C (PLC) pathway play a role in initiating arrestin translocation. Our results show that arrestin translocation can be stimulated by activators of PLC and protein kinase C (PKC), and by cholera toxin in the absence of light. Arrestin translocation to the outer segments is significantly reduced by inhibitors of PLC and PKC. Importantly, we find that treatment with potassium cyanide inhibits arrestin translocation in response to light. Collectively, our results suggest that arrestin translocation is initiated by a G-protein-coupled cascade through PLC and PKC signaling. Furthermore, our results demonstrate that at least the initiation of arrestin translocation requires energy input.

The phototransduction machinery in the rod outer segment has a strong efficacy gradient

PubMed Central

Mazzolini, Monica; Facchetti, Giuseppe; Andolfi, Laura; Proietti Zaccaria, Remo; Tuccio, Salvatore; Treu, Johannes; Altafini, Claudio; Di Fabrizio, Enzo M.; Lazzarino, Marco; Rapp, Gert; Torre, Vincent

2015-01-01

Rod photoreceptors consist of an outer segment (OS) and an inner segment. Inside the OS a biochemical machinery transforms the rhodopsin photoisomerization into electrical signal. This machinery has been treated as and is thought to be homogenous with marginal inhomogeneities. To verify this assumption, we developed a methodology based on special tapered optical fibers (TOFs) to deliver highly localized light stimulations. By using these TOFs, specific regions of the rod OS could be stimulated with spots of light highly confined in space. As the TOF is moved from the OS base toward its tip, the amplitude of saturating and single photon responses decreases, demonstrating that the efficacy of the transduction machinery is not uniform and is 5–10 times higher at the base than at the tip. This gradient of efficacy of the transduction machinery is attributed to a progressive depletion of the phosphodiesterase along the rod OS. Moreover we demonstrate that, using restricted spots of light, the duration of the photoresponse along the OS does not increase linearly with the light intensity as with diffuse light. PMID:25941368

Fine structure of the retinal photoreceptors of the great horned owl (Bubo virginianus).

PubMed

Braekevelt, C R

1993-01-01

The retinal photoreceptors of the great horned owl (Bubo virginianus) consist of rods, single cones and unequal double cones present in a ratio of about 30:1.2. In the light-adapted state the rods are stout cells which are not felt to undergo retinomotor movements. The rod outer segment consists of a stack of scalloped membranous discs enclosed by the cell membrane. The rod inner segment shows an ellipsoid of mitochondria and a wealth of rough endoplasmic reticulum (RER) and polysomes, Golgi zones and autophagic vacuoles but not hyperboloid of glycogen. Single cones show a slightly tapered outer segment, a heterogenous oil droplet and an ellipsoid of mitochondria at the apex of the inner segment. Double cones consist of a larger chief member which also displays an oil droplet and a slightly smaller accessory member which does not. Both members of the double cone as well as the single cone show a prominent ellipsoid, plentiful polysomes and RER and Golgi zones in the inner segment. Neither single nor double cones possess a condensed paraboloid of glycogen but instead show plentiful scattered glycogen particles. Along the contiguous membranes between accessory and chief cones a few presumed junctional complexes are seen near the external limiting membrane. Judging by their morphology in light-adaptation the cones of this species do not undergo photomechanical movements. Rods and cones (both types) have both invaginated (ribbon) and numerous superficial (conventional) synaptic sites. Rods are more numerous in this nocturnally active bird than is usually noted in avian species.

Functional significance of the taper of vertebrate cone photoreceptors

PubMed Central

Hárosi, Ferenc I.

2012-01-01

Vertebrate photoreceptors are commonly distinguished based on the shape of their outer segments: those of cones taper, whereas the ones from rods do not. The functional advantages of cone taper, a common occurrence in vertebrate retinas, remain elusive. In this study, we investigate this topic using theoretical analyses aimed at revealing structure–function relationships in photoreceptors. Geometrical optics combined with spectrophotometric and morphological data are used to support the analyses and to test predictions. Three functions are considered for correlations between taper and functionality. The first function proposes that outer segment taper serves to compensate for self-screening of the visual pigment contained within. The second function links outer segment taper to compensation for a signal-to-noise ratio decline along the longitudinal dimension. Both functions are supported by the data: real cones taper more than required for these compensatory roles. The third function relates outer segment taper to the optical properties of the inner compartment whereby the primary determinant is the inner segment’s ability to concentrate light via its ellipsoid. In support of this idea, the rod/cone ratios of primarily diurnal animals are predicted based on a principle of equal light flux gathering between photoreceptors. In addition, ellipsoid concentration factor, a measure of ellipsoid ability to concentrate light onto the outer segment, correlates positively with outer segment taper expressed as a ratio of characteristic lengths, where critical taper is the yardstick. Depending on a light-funneling property and the presence of focusing organelles such as oil droplets, cone outer segments can be reduced in size to various degrees. We conclude that outer segment taper is but one component of a miniaturization process that reduces metabolic costs while improving signal detection. Compromise solutions in the various retinas and retinal regions occur between ellipsoid size and acuity, on the one hand, and faster response time and reduced light sensitivity, on the other. PMID:22250013

The retina visual cycle is driven by cis retinol oxidation in the outer segments of cones

PubMed Central

Sato, Shinya; Frederiksen, Rikard; Cornwall, M. Carter; Kefalov, Vladimir J.

2017-01-01

Vertebrate rod and cone photoreceptors require continuous supply of chromophore for regenerating their visual pigments after photoactivation. Cones, which mediate our daytime vision, demand a particularly rapid supply of 11-cis retinal chromophore in order to maintain their function in bright light. An important contribution to this process is thought to be the chromophore precursor 11-cis retinol, which is supplied to cones from Müller cells in the retina and subsequently oxidized to 11-cis retinal as part of the retina visual cycle. However, the molecular identity of the cis retinol oxidase in cones remains unclear. Here, as a first step in characterizing this enzymatic reaction, we sought to determine the subcellular localization of this activity in salamander red cones. We found that the onset of dark adaptation of isolated salamander red cones was substantially faster when exposing directly their outer vs. their inner segment to 9-cis retinol, an analogue of 11-cis retinol. In contrast, this difference was not observed when treating the outer vs. inner segment with 9-cis retinal, a chromophore analogue which can directly support pigment regeneration. These results suggest, surprisingly, that the cis-retinol oxidation occurs in the outer segments of cone photoreceptors. Confirming this notion, pigment regeneration with exogenously added 9-cis retinol was directly observed in the truncated outer segments of cones, but not in rods. We conclude that the enzymatic machinery required for the oxidation of recycled cis retinol as part of the retina visual cycle is present in the outer segments of cones. PMID:28359344

The photocurrent, noise and spectral sensitivity of rods of the monkey Macaca fascicularis.

PubMed Central

Baylor, D A; Nunn, B J; Schnapf, J L

1984-01-01

Visual transduction in rods of the cynomolgus monkey, Macaca fascicularis, was studied by recording membrane current from single outer segments projecting from small pieces of retina. Light flashes evoked transient outward-going photocurrents with saturating amplitudes of up to 34 pA. A flash causing twenty to fifty photoisomerizations gave a response of half the saturating amplitude. The response-stimulus relation was of the form 1-e-x where x is flash strength. The response to a dim flash usually had a time to peak of 150-250 ms and resembled the impulse response of a series of six low-pass filters. From the average spectral sensitivity of ten rods the rhodopsin was estimated to have a peak absorption near 491 nm. The spectral sensitivity of the rods was in good agreement with the average human scotopic visibility curve determined by Crawford (1949), when the human curve was corrected for lens absorption and self-screening of rhodopsin. Fluctuations in the photocurrent evoked by dim lights were consistent with a quantal event about 0.7 pA in peak amplitude. A steady light causing about 100 photoisomerizations s-1 reduced the flash sensitivity to half the dark-adapted value. At higher background levels the rod rapidly saturated. These results support the idea that dim background light desensitizes human scotopic vision by a mechanism central to the rod outer segments while scotopic saturation may occur within the outer segments. Recovery of the photocurrent after bright flashes was marked by quantized step-like events. The events had the properties expected if bleached rhodopsin in the disks occasionally caused an abrupt blockage of the dark current over about one-twentieth of the length of the outer segment. It is suggested that superposition of these events after bleaching may contribute to the threshold elevation measured psychophysically. The current in darkness showed random fluctuations which disappeared in bright light. The continuous component of the noise had a variance of about 0.03 pA2 and a power spectrum that fell to half near 3 Hz. A second component, consisting of discrete events resembling single-photon responses, was estimated to occur at a rate of 0.006 s-1. It is suggested that the continuous component of the noise may be removed from scotopic vision by a thresholding operation near the rod output. PMID:6512705

The photocurrent, noise and spectral sensitivity of rods of the monkey Macaca fascicularis.

PubMed

Baylor, D A; Nunn, B J; Schnapf, J L

1984-12-01

Visual transduction in rods of the cynomolgus monkey, Macaca fascicularis, was studied by recording membrane current from single outer segments projecting from small pieces of retina. Light flashes evoked transient outward-going photocurrents with saturating amplitudes of up to 34 pA. A flash causing twenty to fifty photoisomerizations gave a response of half the saturating amplitude. The response-stimulus relation was of the form 1-e-x where x is flash strength. The response to a dim flash usually had a time to peak of 150-250 ms and resembled the impulse response of a series of six low-pass filters. From the average spectral sensitivity of ten rods the rhodopsin was estimated to have a peak absorption near 491 nm. The spectral sensitivity of the rods was in good agreement with the average human scotopic visibility curve determined by Crawford (1949), when the human curve was corrected for lens absorption and self-screening of rhodopsin. Fluctuations in the photocurrent evoked by dim lights were consistent with a quantal event about 0.7 pA in peak amplitude. A steady light causing about 100 photoisomerizations s-1 reduced the flash sensitivity to half the dark-adapted value. At higher background levels the rod rapidly saturated. These results support the idea that dim background light desensitizes human scotopic vision by a mechanism central to the rod outer segments while scotopic saturation may occur within the outer segments. Recovery of the photocurrent after bright flashes was marked by quantized step-like events. The events had the properties expected if bleached rhodopsin in the disks occasionally caused an abrupt blockage of the dark current over about one-twentieth of the length of the outer segment. It is suggested that superposition of these events after bleaching may contribute to the threshold elevation measured psychophysically. The current in darkness showed random fluctuations which disappeared in bright light. The continuous component of the noise had a variance of about 0.03 pA2 and a power spectrum that fell to half near 3 Hz. A second component, consisting of discrete events resembling single-photon responses, was estimated to occur at a rate of 0.006 s-1. It is suggested that the continuous component of the noise may be removed from scotopic vision by a thresholding operation near the rod output.

GUCY2D Cone-Rod Dystrophy-6 Is a "Phototransduction Disease" Triggered by Abnormal Calcium Feedback on Retinal Membrane Guanylyl Cyclase 1.

PubMed

Sato, Shinya; Peshenko, Igor V; Olshevskaya, Elena V; Kefalov, Vladimir J; Dizhoor, Alexander M

2018-03-21

The Arg838Ser mutation in retinal membrane guanylyl cyclase 1 (RetGC1) has been linked to autosomal dominant cone-rod dystrophy type 6 (CORD6). It is believed that photoreceptor degeneration is caused by the altered sensitivity of RetGC1 to calcium regulation via guanylyl cyclase activating proteins (GCAPs). To determine the mechanism by which this mutation leads to degeneration, we investigated the structure and function of rod photoreceptors in two transgenic mouse lines, 362 and 379, expressing R838S RetGC1. In both lines, rod outer segments became shorter than in their nontransgenic siblings by 3-4 weeks of age, before the eventual photoreceptor degeneration. Despite the shortening of their outer segments, the dark current of transgenic rods was 1.5-2.2-fold higher than in nontransgenic controls. Similarly, the dim flash response amplitude in R838S + rods was larger, time to peak was delayed, and flash sensitivity was increased, all suggesting elevated dark-adapted free cGMP in transgenic rods. In rods expressing R838S RetGC1, dark-current noise increased and the exchange current, detected after a saturating flash, became more pronounced. These results suggest disrupted Ca 2+ phototransduction feedback and abnormally high free-Ca 2+ concentration in the outer segments. Notably, photoreceptor degeneration, which typically occurred after 3 months of age in R838S RetGC1 transgenic mice in GCAP1,2 +/+ or GCAP1,2 +/- backgrounds, was prevented in GCAP1,2 -/- mice lacking Ca 2+ feedback to guanylyl cyclase. In summary, the dysregulation of guanylyl cyclase in RetGC1-linked CORD6 is a "phototransduction disease," which means it is associated with increased free-cGMP and Ca 2+ levels in photoreceptors. SIGNIFICANCE STATEMENT In a mouse model expressing human membrane guanylyl cyclase 1 (RetGC1, GUCY2D ), a mutation associated with early progressing congenital blindness, cone-rod dystrophy type 6 (CORD6), deregulates calcium-sensitive feedback of phototransduction to the cyclase mediated by guanylyl cyclase activating proteins (GCAPs), which are calcium-sensor proteins. The abnormal calcium sensitivity of the cyclase increases cGMP-gated dark current in the rod outer segments, reshapes rod photoresponses, and triggers photoreceptor death. This work is the first to demonstrate a direct physiological effect of GUCY2D CORD6-linked mutation on photoreceptor physiology in vivo It also identifies the abnormal regulation of the cyclase by calcium-sensor proteins as the main trigger for the photoreceptor death. Copyright © 2018 the authors 0270-6474/18/382990-11$15.00/0.

Sodium-dependent calcium extrusion and sensitivity regulation in retinal cones of the salamander.

PubMed Central

Nakatani, K; Yau, K W

1989-01-01

1. Membrane current was recorded from an isolated, dark-adapted salamander cone by sucking its inner segment into a tight-fitting glass pipette containing Ringer solution. The outer segment of the cell was exposed to a bath solution that could be changed rapidly. 2. After removing Na+ from the bath Ringer solution for a short period of time in darkness (the 'loading period'), a transient inward current was observed upon restoring it in bright light. A similar but longer-lasting current was observed when Na+ was restored in the light after a large Ca2+ influx was induced through the light-sensitive conductance in darkness. 3. The above transient current was not observed if Li+ or guanidinium was substituted for Na+ in the light, or if Ba2+ was substituted for Ca2+ during the dark loading period. However, a current was observed if Sr2+ was the substituting ion for Ca2+ during loading. These observations suggested that the current was associated with an electrogenic Na+-dependent Ca2+ efflux at the cone outer segment. 4. The saturated amplitude of the exchange current was 12-25 pA with a mean around 16 pA. This is very comparable to that measured in the outer segment of a salamander rod under similar conditions. 5. By comparing a known Ca2+ load in a cone outer segment to the subsequent charge transfer through the exchange, we estimated that the stoichiometry of the exchange was near 3Na+:1Ca2+. 6. With a small Ca2+ load, or in the presence of Cs+ around the inner segment, the final temporal decline of the Na+-Ca2+ exchange current was roughly exponential, with a mean time constant of about 100 ms. This decline is about four times faster than that measured in rods. We interpret the shorter time constant in cones to reflect a faster rate of decline of intracellular free Ca2+ in their outer segments resulting from the exchange activity. 7. In the absence of external Na+, and hence any Na+-dependent Ca2+ efflux, the absolute sensitivity of a cone to a dim flash was several times higher than in normal Ringer solution. 8. A roughly similar increase in light sensitivity was observed for a rod under the same conditions. 9. We conclude that the Na+-dependent Ca2+ efflux, through lowering intracellular free Ca2+ in the light, has a role in regulating the absolute light sensitivity in cones as it does in rods.(ABSTRACT TRUNCATED AT 400 WORDS) PMID:2479741

The effect of light on outer segment calcium in salamander rods

PubMed Central

Matthews, Hugh R; Fain, Gordon L

2003-01-01

Calcium acts as a second messenger in vertebrate rods, regulating the recovery phase of the light response and modulating sensitivity during light-adaptation. Since light not only decreases the outer segment calcium concentration ([Ca2+]i) by closing cyclic nucleotide-gated channels but can also increase [Ca2+]i by releasing Ca2+ from buffer sites or intracellular stores, we examined in detail the effect of light and circulating current on [Ca2+]i by making simultaneous measurements of suction pipette current and [Ca2+]i from isolated rods of the salamander Ambystoma tigrinum after incorporation of the fluorescent dye fluo-5F. When the release of Ca2+ is measured in 0 Ca2+−0 Na+ solution, minimising fluxes of Ca2+ across the plasma membrane, it is substantial only for light bright enough to bleach a significant fraction of the photopigment and is restricted to the part of the outer segment in which the bleach occurred. It is unlikely, therefore, to make a large contribution to [Ca2+]i for most of the physiological operating range of the rod. Nevertheless, since release is half-maximal for a bleach of less than 10 %, it cannot be produced by a simple mechanism such as a change in the affinity of a binding site on rhodopsin itself but must instead require some more complex interaction. In Ringer solution, the Ca2+ in the light-releasable pool can be discharged merely by the decrease in [Ca2+]i that occurs as the outer segment channels close. In steady background light or after exposure to saturating illumination, the fraction of Ca2+ in the pool decreases essentially in proportion to [Ca2+]i as if Ca2+ were being removed from a buffer site within the cytoplasm. Furthermore, [Ca2+]i itself changes in proportion to the circulating current, with little evidence for a contribution from Ca2+ release or other mechanisms of Ca2+ homeostasis. This indicates that flux of Ca2+ across the plasma membrane is the major determinant of outer segment Ca2+ concentration within the rod's normal operating light intensity range. Once Ca2+ has been discharged from the releasable pool, it is restored following dim illumination apparently as the simple result of the subsequent restoration of dark [Ca2+]i and the rebinding of Ca2+ to its release site, but after brighter light perhaps also as a consequence of regeneration of the photopigment. PMID:12949220

Pineal organs of deep-sea fish: photopigments and structure.

PubMed

Bowmaker, James K; Wagner, Hans-Joachim

2004-06-01

We have examined the morphology and photopigments of the pineal organs from a number of mesopelagic fish, including representatives of the hatchet fish (Sternoptychidae), scaly dragon-fish (Chauliodontidae) and bristlemouths (Gonostomidae). Although these fish were caught at depths of between 500 and 1000 m, the morphological organisation of their pineal organs is remarkably similar to that of surface-dwelling fish. Photoreceptor inner and outer segments protrude into the lumen of the pineal vesicle, and the outer segment is composed of a stack of up to 20 curved disks that form a cap-like cover over the inner segment. In all species, the pineal photopigment was spectrally distinct from the retinal rod pigment, with lambdamax displaced to longer wavelengths, between approximately 485 and 503 nm. We also investigated the pineal organ of the deep demersal eel, Synaphobranchus kaupi, caught at depths below 2000 m, which possesses a rod visual pigment with lambdamax at 478 nm, but the pineal pigment has lambdamax at approximately 515 nm. In one species of hatchet fish, Argyropelecus affinis, two spectral classes of pinealocyte were identified, both spectrally distinct from the retinal rod photopigment.

Physiological and Microfluorometric Studies of Reduction and Clearance of Retinal in Bleached Rod Photoreceptors

PubMed Central

Tsina, Efthymia; Chen, Chunhe; Koutalos, Yiannis; Ala-Laurila, Petri; Tsacopoulos, Marco; Wiggert, Barbara; Crouch, Rosalie K.; Cornwall, M. Carter

2004-01-01

The visual cycle comprises a sequence of reactions that regenerate the visual pigment in photoreceptors during dark adaptation, starting with the reduction of all-trans retinal to all-trans retinol and its clearance from photoreceptors. We have followed the reduction of retinal and clearance of retinol within bleached outer segments of red rods isolated from salamander retina by measuring its intrinsic fluorescence. Following exposure to a bright light (bleach), increasing fluorescence intensity was observed to propagate along the outer segments in a direction from the proximal region adjacent to the inner segment toward the distal tip. Peak retinol fluorescence was achieved after ∼30 min, after which it declined very slowly. Clearance of retinol fluorescence is considerably accelerated by the presence of the exogenous lipophilic substances IRBP (interphotoreceptor retinoid binding protein) and serum albumin. We have used simultaneous fluorometric and electrophysiological measurements to compare the rate of reduction of all-trans retinal to all-trans retinol to the rate of recovery of flash response amplitude in these cells in the presence and absence of IRBP. We find that flash response recovery in rods is modestly accelerated in the presence of extracellular IRBP. These results suggest such substances may participate in the clearance of retinoids from rod photoreceptors, and that this clearance, at least in rods, may facilitate dark adaptation by accelerating the clearance of photoproducts of bleaching. PMID:15452202

Effects of ionizing radiation on the light sensing elements of the retina. [Structural and physiological effects of carbon, helium, and neon ions on rods and cones of salamanders and mice

DOE Office of Scientific and Technical Information (OSTI.GOV)

Malachowski, M.J.

1978-07-01

This investigation was undertaken to quantitate possible morphological and physiological effects of particles of high linear energy transfer on the retina, in comparison with x-ray effects. The particles used were accelerated atomic nuclei of helium, carbon, and neon at kinetic energies of several hundred MeV/nucleon. For morphological studies, scanning and transmission electron microscopy and light microscopy were used. Physiological studies consisted of autoradiographic data of the rate of incorporation of labeled protein in the structures (opsin) of the outer segment of visual cells. Structural changes were found in the nuclei, as well as the inner and outer segments of visualmore » cells, rods and cones. At a low dose of 10 rad, x rays and helium had no statistically significant morphological effects, but carbon and neon beams did cause significant degeneration of individual cells, pointing to the existence of a linear dose--effect relationship. At high doses of several hundred rads, a Pathologic Index determined the relative biological effectiveness of neon against alpha particles to have a value of greater than 6. The severity of effects per particle increased with atomic number. Labeling studies demonstrated a decreased rate of incorporation of labeled proteins in the structural organization of the outer segments of visual rods. The rate of self-renewal of visual rod discs was punctuated by irradiation and the structures themselves were depleted of amino acids. A model of rod discs (metabolic and catabolic) was postulated for correlated early and late effects to high and low doses.« less

Rescue of mutant rhodopsin traffic by metformin-induced AMPK activation accelerates photoreceptor degeneration

PubMed Central

Athanasiou, Dimitra; Aguila, Monica; Opefi, Chikwado A.; South, Kieron; Bellingham, James; Bevilacqua, Dalila; Munro, Peter M.; Kanuga, Naheed; Mackenzie, Francesca E.; Dubis, Adam M.; Georgiadis, Anastasios; Graca, Anna B.; Pearson, Rachael A.; Ali, Robin R.; Sakami, Sanae; Palczewski, Krzysztof; Sherman, Michael Y.; Reeves, Philip J.

2017-01-01

Abstract Protein misfolding caused by inherited mutations leads to loss of protein function and potentially toxic ‘gain of function’, such as the dominant P23H rhodopsin mutation that causes retinitis pigmentosa (RP). Here, we tested whether the AMPK activator metformin could affect the P23H rhodopsin synthesis and folding. In cell models, metformin treatment improved P23H rhodopsin folding and traffic. In animal models of P23H RP, metformin treatment successfully enhanced P23H traffic to the rod outer segment, but this led to reduced photoreceptor function and increased photoreceptor cell death. The metformin-rescued P23H rhodopsin was still intrinsically unstable and led to increased structural instability of the rod outer segments. These data suggest that improving the traffic of misfolding rhodopsin mutants is unlikely to be a practical therapy, because of their intrinsic instability and long half-life in the outer segment, but also highlights the potential of altering translation through AMPK to improve protein function in other protein misfolding diseases. PMID:28065882

Meckelin 3 Is Necessary for Photoreceptor Outer Segment Development in Rat Meckel Syndrome

PubMed Central

Tiwari, Sarika; Hudson, Scott; Gattone, Vincent H.; Miller, Caroline; Chernoff, Ellen A. G.; Belecky-Adams, Teri L.

2013-01-01

Ciliopathies lead to multiorgan pathologies that include renal cysts, deafness, obesity and retinal degeneration. Retinal photoreceptors have connecting cilia joining the inner and outer segment that are responsible for transport of molecules to develop and maintain the outer segment process. The present study evaluated meckelin (MKS3) expression during outer segment genesis and determined the consequences of mutant meckelin on photoreceptor development and survival in Wistar polycystic kidney disease Wpk/Wpk rat using immunohistochemistry, analysis of cell death and electron microscopy. MKS3 was ubiquitously expressed throughout the retina at postnatal day 10 (P10) and P21. However, in the mature retina, MKS3 expression was restricted to photoreceptors and the retinal ganglion cell layer. At P10, both the wild type and homozygous Wpk mutant retina had all retinal cell types. In contrast, by P21, cells expressing rod- and cone-specific markers were fewer in number and expression of opsins appeared to be abnormally localized to the cell body. Cell death analyses were consistent with the disappearance of photoreceptor-specific markers and showed that the cells were undergoing caspase-dependent cell death. By electron microscopy, P10 photoreceptors showed rudimentary outer segments with an axoneme, but did not develop outer segment discs that were clearly present in the wild type counterpart. At p21 the mutant outer segments appeared much the same as the P10 mutant outer segments with only a short axoneme, while the wild-type controls had developed outer segments with many well-organized discs. We conclude that MKS3 is not important for formation of connecting cilium and rudimentary outer segments, but is critical for the maturation of outer segment processes. PMID:23516626

The Photosensitivity of Rhodopsin Bleaching and Light-Induced Increases of Fundus Reflectance in Mice Measured In Vivo With Scanning Laser Ophthalmoscopy

PubMed Central

Zhang, Pengfei; Goswami, Mayank; Zawadzki, Robert J.; Pugh, Edward N.

2016-01-01

Purpose To quantify bleaching-induced changes in fundus reflectance in the mouse retina. Methods Light reflected from the fundus of albino (Balb/c) and pigmented (C57Bl/6J) mice was measured with a multichannel scanning laser ophthalmoscopy optical coherence tomography (SLO-OCT) optical system. Serial scanning of small retinal regions was used for bleaching rhodopsin and measuring reflectance changes. Results Serial scanning generated a saturating reflectance increase centered at 501 nm with a photosensitivity of 1.4 × 10−8 per molecule μm2 in both strains, 2-fold higher than expected were irradiance at the rod outer segment base equal to that at the retinal surface. The action spectrum of the reflectance increase corresponds to the absorption spectrum of mouse rhodopsin in situ. Spectra obtained before and after bleaching were fitted with a model of fundus reflectance, quantifying contributions from loss of rhodopsin absorption with bleaching, absorption by oxygenated hemoglobin (HbO2) in the choroid (Balb/c), and absorption by melanin (C57Bl/6J). Both mouse strains exhibited light-induced broadband reflectance changes explained as bleaching-induced reflectivity increases at photoreceptor inner segment/outer segment (IS/OS) junctions and OS tips. Conclusions The elevated photosensitivity of rhodopsin bleaching in vivo is explained by waveguide condensing of light in propagation from rod inner segment (RIS) to rod outer segment (ROS). The similar photosensitivity of rhodopsin in the two strains reveals that little light backscattered from the sclera can enter the ROS. The bleaching-induced increases in reflectance at the IS/OS junctions and OS tips resemble results previously reported in human cones, but are ascribed to rods due to their 30/1 predominance over cones in mice and to the relatively minor amount of cone M-opsin in the regions scanned. PMID:27403994

Abnormal photoreceptor outer segment development and early retinal degeneration in kif3a mutant zebrafish.

PubMed

Raghupathy, Rakesh K; Zhang, Xun; Alhasani, Reem H; Zhou, Xinzhi; Mullin, Margaret; Reilly, James; Li, Wenchang; Liu, Mugen; Shu, Xinhua

2016-08-01

Photoreceptors are highly specialized sensory neurons that possess a modified primary cilium called the outer segment. Photoreceptor outer segment formation and maintenance require highly active protein transport via a process known as intraflagellar transport. Anterograde transport in outer segments is powered by the heterotrimeric kinesin II and coordinated by intraflagellar transport proteins. Here, we describe a new zebrafish model carrying a nonsense mutation in the kinesin II family member 3A (kif3a) gene. Kif3a mutant zebrafish exhibited curved body axes and kidney cysts. Outer segments were not formed in most parts of the mutant retina, and rhodopsin was mislocalized, suggesting KIF3A has a role in rhodopsin trafficking. Both rod and cone photoreceptors degenerated rapidly between 4 and 9 days post fertilization, and electroretinography response was not detected in 7 days post fertilization mutant larvae. Loss of KIF3A in zebrafish also resulted in an intracellular transport defect affecting anterograde but not retrograde transport of organelles. Our results indicate KIF3A plays a conserved role in photoreceptor outer segment formation and intracellular transport. Copyright © 2016 John Wiley & Sons, Ltd.

Glycolytic reliance promotes anabolism in photoreceptors

PubMed Central

Chinchore, Yashodhan; Begaj, Tedi; Wu, David; Drokhlyansky, Eugene; Cepko, Constance L

2017-01-01

Vertebrate photoreceptors are among the most metabolically active cells, exhibiting a high rate of ATP consumption. This is coupled with a high anabolic demand, necessitated by the diurnal turnover of a specialized membrane-rich organelle, the outer segment, which is the primary site of phototransduction. How photoreceptors balance their catabolic and anabolic demands is poorly understood. Here, we show that rod photoreceptors in mice rely on glycolysis for their outer segment biogenesis. Genetic perturbations targeting allostery or key regulatory nodes in the glycolytic pathway impacted the size of the outer segments. Fibroblast growth factor signaling was found to regulate glycolysis, with antagonism of this pathway resulting in anabolic deficits. These data demonstrate the cell autonomous role of the glycolytic pathway in outer segment maintenance and provide evidence that aerobic glycolysis is part of a metabolic program that supports the biosynthetic needs of a normal neuronal cell type. DOI: http://dx.doi.org/10.7554/eLife.25946.001 PMID:28598329

Segmented inlet nozzle for gas turbine, and methods of installation

DOEpatents

Klompas, Nicholas

1985-01-01

A gas turbine nozzle guide vane assembly is formed of individual arcuate nozzle segments. The arcuate nozzle segments are elastically joined to each other to form a complete ring, with edges abutted to prevent leakage. The resultant nozzle ring is included within the overall gas turbine stationary structure and secured by a mounting arrangement which permits relative radial movement at both the inner and outer mountings. A spline-type outer mounting provides circumferential retention. A complete rigid nozzle ring with freedom to "float" radially results. Specific structures are disclosed for the inner and outer mounting arrangements. A specific tie-rod structure is also disclosed for elastically joining the individual nozzle segments. Also disclosed is a method of assembling the nozzle ring subassembly-by-subassembly into a gas turbine employing temporary jacks.

Adaptations in rod outer segment disc membranes in response to environmental lighting conditions.

PubMed

Rakshit, Tatini; Senapati, Subhadip; Parmar, Vipul M; Sahu, Bhubanananda; Maeda, Akiko; Park, Paul S-H

2017-10-01

The light-sensing rod photoreceptor cell exhibits several adaptations in response to the lighting environment. While adaptations to short-term changes in lighting conditions have been examined in depth, adaptations to long-term changes in lighting conditions are less understood. Atomic force microscopy was used to characterize the structure of rod outer segment disc membranes, the site of photon absorption by the pigment rhodopsin, to better understand how photoreceptor cells respond to long-term lighting changes. Structural properties of the disc membrane changed in response to housing mice in constant dark or light conditions and these adaptive changes required output from the phototransduction cascade initiated by rhodopsin. Among these were changes in the packing density of rhodopsin in the membrane, which was independent of rhodopsin synthesis and specifically affected scotopic visual function as assessed by electroretinography. Studies here support the concept of photostasis, which maintains optimal photoreceptor cell function with implications in retinal degenerations. Copyright © 2017 Elsevier B.V. All rights reserved.

Histological techniques for study of photoreceptor orientation.

PubMed

Laties, A M

1969-01-01

An histological method for the study of photoreceptor orientation in primate eyes is described. To preserve photoreceptor orientation it is necessary to protect the fragile rod and cone outer segments to the maximum extent possible from mechanical deformation and from injury by solvent extraction. To prevent mechanical deformation the eyes are freeze-dried and embedded in plastic with or without prior vapor fixation. Solvent extraction from the lipid-rich outer segment is limited by avoidance or restriction of organic solvents. When large segments of primate eyes are so treated, it is possible to section the plastic blocks along the visual axis, polish the block surface, and view photoreceptor orientation by epi-illumination microscopy. In such specimens a differential orientation of photoreceptors exists with the long axis of photoreceptor inner and outer segments in line with incoming light rays.

Cytologic appearance of retinal cells included in a fine-needle aspirate of a meningioma around the optic nerve of a dog.

PubMed

Tvedten, Harold; Hillström, Anna

2013-06-01

A 6-year-old Wirehair Dachshund had a meningioma around the optic nerve that caused exophthalmos. A benign mesenchymal tumor was suspected based on the cytologic pattern of a fine-needle aspirate, and a meningioma was diagnosed by histopathologic examination. In addition to the meningioma cells, the cytologic smears included groups of cells from apparently 4 layers of normal retina. In particular, uniform rod-shaped structures in the cytologic sample could suggest rod-shaped bacteria, but these structures were identified as cylindrical outer segments of photoreceptor rod cells. Other retinal structures recognized included pigmented epithelial layer cells with their uniquely formed pigment granules, the characteristic bi-lobed, cleaved nuclei from the outer nuclear layer, and nerve tissue likely from the outer plexiform layer of the retina. © 2013 American Society for Veterinary Clinical Pathology.

Longitudinal assessment of retinal structure and function reveals a rod-cone degeneration in a guinea pig model initially presented as night blind.

PubMed

Racine, Julie; Joly, Sandrine; Lachapelle, Pierre

2011-08-01

We have previously reported a naturally occurring retinopathy in a population of guinea pigs, where the affected animals presented a defect of the rod-mediated vision. The purpose of this study was to investigate if the mutants were affected with a stationary or degenerative retinopathy and to identify the cellular origin of this unique disorder. Electroretinogram (ERG) [postnatal day 1 (P1) to P450], light (LM) and electron microscopy (EM) [P5, P150, P450], and immunohistochemistry [P30, P150, P450] were evaluated from normal and mutant animals. Irrespective of age, the scotopic ERGs of mutants could only be evoked by bright flashes, and the resulting ERGs were of photopic waveform. Interestingly, the amplitude of the cone and the rod/cone a-waves was always of smaller amplitude in mutants, but this difference tended to decrease with age. In contrast, the b-waves were of larger amplitude than normal in photopic ERGs obtained prior to age 25 (days) and prior to age 10 for rod/cone ERGs. LM revealed, in mutants, an absence of the outer segment layer (OSL) with a reduction in the outer nuclear layer (ONL) thickness. EM disclosed the presence of cone outer segment (OS) while no rod OS could be evidenced. Immunohistochemistry revealed the presence of rhodopsin, both cone opsins as well as normal synaptophysin immunoreactivity. Finally, neither the retinal structure nor the function in the mutants achieved normal development. Results suggest that mutant animals are suffering from a degenerative retinal disorder that affects the structure and function of rods and cones.

A new mouse model for stationary night blindness with mutant Slc24a1 explains the pathophysiology of the associated human disease

PubMed Central

Vinberg, Frans; Wang, Tian; Molday, Robert S.; Chen, Jeannie; Kefalov, Vladimir J.

2015-01-01

Mutations that affect calcium homeostasis (Ca2+) in rod photoreceptors are linked to retinal degeneration and visual disorders such as retinitis pigmentosa and congenital stationary night blindness (CSNB). It is thought that the concentration of Ca2+ in rod outer segments is controlled by a dynamic balance between influx via cGMP-gated (CNG) channels and extrusion via Na+/Ca2+, K+ exchangers (NCKX1). The extrusion-driven lowering of rod [Ca2+]i following light exposure controls their light adaptation and response termination. Mutant NCKX1 has been linked to autosomal-recessive stationary night blindness. However, whether NCKX1 contributes to light adaptation has not been directly tested and the mechanisms by which human NCKX1 mutations cause night blindness are not understood. Here, we report that the deletion of NCKX1 in mice results in malformed outer segment disks, suppressed expression and function of rod CNG channels and a subsequent 100-fold reduction in rod responses, while preserving normal cone responses. The compensating loss of CNG channel function in the absence of NCKX1-mediated Ca2+ extrusion may prevent toxic Ca2+ buildup and provides an explanation for the stationary nature of the associated disorder in humans. Surprisingly, the lack of NCKX1 did not compromise rod background light adaptation, suggesting additional Ca2+-extruding mechanisms exist in these cells. PMID:26246500

Rod outer segment retinol formation is independent of Abca4, arrestin, rhodopsin kinase, and rhodopsin palmitylation.

PubMed

Blakeley, Lorie R; Chen, Chunhe; Chen, Ching-Kang; Chen, Jeannie; Crouch, Rosalie K; Travis, Gabriel H; Koutalos, Yiannis

2011-06-01

The reactive aldehyde all-trans retinal is released in rod photoreceptor outer segments by photoactivated rhodopsin and is eliminated through reduction to all-trans retinol. This study was undertaken to determine whether all-trans retinol formation depends on Abca4, arrestin, rhodopsin kinase, and the palmitylation of rhodopsin, all of which are factors that affect the release and sequestration of all-trans retinal. Experiments were performed in isolated retinas and single living rods derived from 129/sv wild-type mice and Abca4-, arrestin-, and rhodopsin kinase-deficient mice and in genetically modified mice containing unpalmitylated rhodopsin. Formation of all-trans retinol was measured by imaging its fluorescence and by HPLC of retina extracts. The release of all-trans retinal from photoactivated rhodopsin was measured in purified rod outer segment membranes according to the increase in tryptophan fluorescence. All experiments were performed at 37°C. The kinetics of all-trans retinol formation in the different types of genetically modified mice are in reasonable agreement with those in wild-type animals. The kinetics of all-trans retinol formation in 129/sv mice are similar to those in C57BL/6, although the latter are known to regenerate rhodopsin much more slowly. The release of all-trans retinal from rhodopsin in purified membranes is significantly faster than the formation of all-trans retinol in intact cells and is independent of the presence of the palmitate groups. The regeneration of rhodopsin and the recycling of its chromophore are not strongly coupled. Neither the activities of Abca4, rhodopsin kinase, and arrestin, nor the palmitylation of rhodopsin affects the formation of all-trans retinol.

Interaction of 4.1G and cGMP-gated channels in rod photoreceptor outer segments.

PubMed

Cheng, Christiana L; Molday, Robert S

2013-12-15

In photoreceptors, the assembly of signaling molecules into macromolecular complexes is important for phototransduction and maintaining the structural integrity of rod outer segments (ROSs). However, the molecular composition and formation of these complexes are poorly understood. Using immunoprecipitation and mass spectrometry, 4.1G was identified as a new interacting partner for the cyclic-nucleotide gated (CNG) channels in ROSs. 4.1G is a widely expressed multifunctional protein that plays a role in the assembly and stability of membrane protein complexes. Multiple splice variants of 4.1G were cloned from bovine retina. A smaller splice variant of 4.1G selectively interacted with CNG channels not associated with peripherin-2-CNG channel complex. A combination of truncation studies and domain-binding assays demonstrated that CNG channels selectively interacted with 4.1G through their FERM and CTD domains. Using immunofluorescence, labeling of 4.1G was seen to be punctate and partially colocalized with CNG channels in the ROS. Our studies indicate that 4.1G interacts with a subset of CNG channels in the ROS and implicate this protein-protein interaction in organizing the spatial arrangement of CNG channels in the plasma membrane of outer segments.

A key role for cyclic nucleotide gated (CNG) channels in cGMP-related retinitis pigmentosa.

PubMed

Paquet-Durand, François; Beck, Susanne; Michalakis, Stylianos; Goldmann, Tobias; Huber, Gesine; Mühlfriedel, Regine; Trifunović, Dragana; Fischer, M Dominik; Fahl, Edda; Duetsch, Gabriele; Becirovic, Elvir; Wolfrum, Uwe; van Veen, Theo; Biel, Martin; Tanimoto, Naoyuki; Seeliger, Mathias W

2011-03-01

The rd1 natural mutant is one of the first and probably the most commonly studied mouse model for retinitis pigmentosa (RP), a severe and frequently blinding human retinal degeneration. In several decades of research, the link between the increase in photoreceptor cGMP levels and the extremely rapid cell death gave rise to a number of hypotheses. Here, we provide clear evidence that the presence of cyclic nucleotide gated (CNG) channels in the outer segment membrane is the key to rod photoreceptor loss. In Cngb1(-/-) × rd1 double mutants devoid of regular CNG channels, cGMP levels are still pathologically high, but rod photoreceptor viability and outer segment morphology are greatly improved. Importantly, cone photoreceptors, the basis for high-resolution daylight and colour vision, survived and remained functional for extended periods of time. These findings strongly support the hypothesis of deleterious calcium (Ca(2+))-influx as the cause of rapid rod cell death and highlight the importance of CNG channels in this process. Furthermore, our findings suggest that targeting rod CNG channels, rather than general Ca(2+)-channel blockade, is a most promising symptomatic approach to treat otherwise incurable forms of cGMP-related RP.

Differentiation of Swine iPSC into Rod Photoreceptors and Their Integration into the Retina

PubMed Central

Zhou, Liang; Wang, Wei; Liu, Yongqing; de Castro, Juan Fernandez; Ezashi, Toshihiko; Telugu, Bhanu Prakash V.L.; Roberts, R. Michael; Kaplan, Henry J.; Dean, Douglas C.

2014-01-01

Absence of a regenerative pathway for damaged retina following injury or disease has led to experiments utilizing stem cell transplantation for retinal repair, and encouraging results have been obtained in rodents. The swine eye is a closer anatomical and physiological match to the human eye, but embryonic stem cells have not been isolated from pig, and photoreceptor differentiation has not been demonstrated with swine induced pluripotent stem cells (iPSC). Here, we subjected swine iPSC to a rod photoreceptor differentiation protocol consisting of floating culture as embryoid bodies followed by differentiation in adherent culture. Real time PCR and immunostaining of differentiated cells demonstrated loss of expression of the pluripotent genes POU5F1, NANOG and SOX2 and induction of rod photoreceptor genes RCVRN, NRL, RHO and ROM1. While these differentiated cells displayed neuronal morphology, culturing on a Matrigel substratum triggered a further morphological change resulting in concentration of RHO and ROM1 in outer segment-like projections resembling those on primary cultures of rod photoreceptors. The differentiated cells were transplanted into the subretinal space of pigs treated with iodoacetic acid to eliminate rod photoreceptors. Three weeks after transplantation, engrafted RHO+ cells were evident in the outer nuclear layer where photoreceptors normally reside. A portion of these transplanted cells had generated projections resembling outer segments. These results demonstrate that swine iPSC can differentiate into photoreceptors in culture and these cells can integrate into the damaged swine neural retina thus laying a foundation for future studies using the pig as a model for retinal stem cell transplantation. PMID:21491544

Role of subunit assembly in autosomal dominant retinitis pigmentosa linked to mutations in peripherin 2.

PubMed

Molday, Robert S; Molday, Laurie L; Loewen, Christopher J R

2004-01-01

Peripherin 2 is a photoreceptor-specific membrane protein implicated in outer segment disk morphogenesis and linked to various retinopathies including autosomal dominant retinitis pigmentosa (ADRP). Peripherin 2 and ROM1 assemble as a mixture of core noncovalent homomeric and heteromeric tetramers that further link together through disulfide bonds to form higher order oligomers. These complexes are critical for disk rim formation and outer segment structure through interaction with the cGMP-gated channel and other photoreceptor proteins. We have examined the role of subunit assembly in peripherin 2 targeting to disks, outer segment structure, and photoreceptor degeneration by examining molecular and cellular properties of peripherin 2 mutants in COS-1 cells and transgenic Xenopus laevis rod photoreceptors. Wild-type (WT) and the ADRP-linked P216L mutant were transported and incorporated into newly formed outer segment disks of transgenic X. laevis. The P216L mutant, however, induced progressive outer segment instability and photoreceptor degeneration possibly through the introduction of a new N-linked oligosaccharide chain. In contrast, the C214S and L185P disease-linked, tetramerization-defective mutants, were retained in the inner segment, but did not affect outer segment structure or induce photoreceptor degeneration. Together, these results indicate that peripherin 2 mutations can cause ADRP either through a deficiency in WT peripherin 2 (C214S, 1.185P) or by a dominant negative effect on disk stability (P216L).

Transducin β-Subunit Can Interact with Multiple G-Protein γ-Subunits to Enable Light Detection by Rod Photoreceptors.

PubMed

Dexter, Paige M; Lobanova, Ekaterina S; Finkelstein, Stella; Spencer, William J; Skiba, Nikolai P; Arshavsky, Vadim Y

2018-01-01

The heterotrimeric G-protein transducin mediates visual signaling in vertebrate photoreceptor cells. Many aspects of the function of transducin were learned from knock-out mice lacking its individual subunits. Of particular interest is the knockout of its rod-specific γ-subunit (Gγ 1 ). Two studies using independently generated mice documented that this knockout results in a considerable >60-fold reduction in the light sensitivity of affected rods, but provided different interpretations of how the remaining α-subunit (Gα t ) mediates phototransduction without its cognate Gβ 1 γ 1 -subunit partner. One study found that the light sensitivity reduction matched a corresponding reduction in Gα t content in the light-sensing rod outer segments and proposed that Gα t activation is supported by remaining Gβ 1 associating with other Gγ subunits naturally expressed in photoreceptors. In contrast, the second study reported the same light sensitivity loss but a much lower, only approximately sixfold, reduction of Gα t and proposed that the light responses of these rods do not require Gβγ at all. To resolve this controversy and elucidate the mechanism driving visual signaling in Gγ 1 knock-out rods, we analyzed both mouse lines side by side. We first determined that the outer segments of both mice have identical Gα t content, which is reduced ∼65-fold from the wild-type (WT) level. We further demonstrated that the remaining Gβ 1 is present in a complex with endogenous Gγ 2 and Gγ 3 subunits and that these complexes exist in wild-type rods as well. Together, these results argue against the idea that Gα t alone supports light responses of Gγ 1 knock-out rods and suggest that Gβ 1 γ 1 is not unique in its ability to mediate vertebrate phototransduction.

Development of an MRI biomarker sensitive to tetrameric visual arrestin 1 and its reduction via light-evoked translocation in vivo.

PubMed

Berkowitz, Bruce A; Gorgis, Jawan; Patel, Ankit; Baameur, Faiza; Gurevich, Vsevolod V; Craft, Cheryl M; Kefalov, Vladimir J; Roberts, Robin

2015-02-01

Rod tetrameric arrestin 1 (tet-ARR1), stored in the outer nuclear layer/inner segments in the dark, modulates photoreceptor synaptic activity; light exposure stimulates a reduction via translocation to the outer segments for terminating G-protein coupled phototransduction signaling. Here, we test the hypothesis that intraretinal spin-lattice relaxation rate in the rotating frame (1/T1ρ), an endogenous MRI contrast mechanism, has high potential for evaluating rod tet-ARR1 and its reduction via translocation. Dark- and light-exposed mice (null for the ARR1 gene, overexpressing ARR1, diabetic, or wild type with or without treatment with Mn2+, a calcium channel probe) were studied using 1/T1ρ MRI. Immunohistochemistry and single-cell recordings of the retinas were also performed. In wild-type mice with or without treatment with Mn2+, 1/T1ρ of avascular outer retina (64% to 72% depth) was significantly (P < 0.05) greater in the dark than in the light; a significant (P < 0.05) but opposite pattern was noted in the inner retina (<50% depth). Light-evoked outer retina Δ1/T1ρ was absent in ARR1-null mice and supernormal in overexpressing mice. In diabetic mice, the outer retinal Δ1/T1ρ pattern suggested normal dark-to-light tet-ARR1 translocation and chromophore content, conclusions confirmed ex vivo. Light-stimulated Δ1/T1ρ in inner retina was linked to changes in blood volume. Our data support 1/T1ρ MRI for noninvasively assessing rod tet-ARR1 and its reduction via protein translocation, which can be combined with other metrics of retinal function in vivo. © FASEB.

Lateral diffusion of rhodopsin in photoreceptor membrane: a reappraisal.

PubMed

Govardovskii, Victor I; Korenyak, Darya A; Shukolyukov, Sergei A; Zueva, Lidia V

2009-08-28

In a series of works between 1972 and 1984, it was established that rhodopsin undergoes rotational and lateral Brownian motion in the plane of photoreceptor membrane. The concept of free movement of proteins of phototransduction cascade is an essential principle of the present scheme of vertebrate phototransduction. This has recently been challenged by findings that show that in certain conditions rhodopsin in the membrane may be dimeric and form extended areas of paracrystalline organization. Such organization seems incompatible with earlier data on free rhodopsin diffusion. Thus we decided to reinvestigate lateral diffusion of rhodopsin and products of its photolysis in photoreceptor membrane specifically looking for indications of possible oligomeric organization. Diffusion exchange by rhodopsin and its photoproducts between bleached and unbleached halves of rod outer segment was traced using high-speed dichroic microspectrophotometer. Measurements were conducted on amphibian (frog, toad, and salamander) and gecko rods. We found that the curves that are supposed to reflect the process of diffusion equilibration of rhodopsin in nonuniformly bleached outer segment largely show production of long-lived bleaching intermediate, metarhodopsin III (Meta III). After experimental elimination of Meta III contribution, we observed rhodopsin equilibration time constant was threefold to tenfold longer than estimated previously. However, after proper correction for the geometry of rod discs, it translates into generally accepted value of diffusion constant of approximately 5 x 10(-9) cm(2) s(-1). Yet, we found that there exists an immobile rhodopsin fraction whose size can vary from virtually zero to 100%, depending on poorly defined factors. Controls suggest that the formation of the immobile fraction is not due to fragmentation of rod outer segment discs but supposedly reflects oligomerization of rhodopsin. Implications of the new findings for the present model of phototransduction are discussed. We hypothesize that formation of paracrystalline areas, if controlled physiologically, could be an extra mechanism of cascade regulation.

Cone outer segment and Müller microvilli pericellular matrices provide binding domains for interphotoreceptor retinoid-binding protein (IRBP).

PubMed

Garlipp, Mary Alice; Gonzalez-Fernandez, Federico

2013-08-01

The close packing of vertebrate photoreceptors presents a challenge to the exchange of molecules between the outer segments, retinal pigmented epithelium (RPE), and Müller glia. An extracellular hyaluronan scaffold separates these cells while soluble interphotoreceptor matrix (IPM) proteins traffic visual cycle retinoids, fatty acids, and other molecules between them. In the IPM, retinoids and fatty acids are carried by interphotoreceptor retinoid-binding protein (IRBP). The fact that much of the retina's IRBP can be extracted by saline wash has led to the notion that IRBP does not bind to the retina, but freely distributes itself within the subretinal space. In this study, we challenge this idea by asking if there are specialized IPM domains that bind IRBP, perhaps facilitating its ability to target delivery/uptake of its ligands. Xenopus is an ideal animal model to study the role of the IPM in RPE-photoreceptor interactions. Here, we took advantage of the large size of its photoreceptors, ability to detach the retina in light, sustainability of the retina in short term organ culture, and the availability of recombinant full-length Xenopus IRBP and antisera directed against Xenopus IRBP. We compared the distribution of wash resistant native IRBP, and that of IRBP-Alexa 647 binding in Xenopus retina. IRBP and cone opsin were localized using anti-Xenopus IRBP serum, and monoclonal COS-1 respectively. Cone matrix sheath proteoglycans were localized with wheat germ agglutinin (WGA), and diffuse IPM proteoglycans with peanut agglutinin (PNA). Wholemounts and frozen sections were compared by immunofluorescence from retinas detached under Ringer's followed by additional washes, or detached directly under 4% paraformaldehyde without Ringer's wash. Undetached Lowicryl embedded retinas were subjected to IRBP immunogold electron microscopy (EM). Immunogold labeled a diffuse network of filamentous structures, and a separate distinct flocculant material directly coating the outer segments, filling the rod periciliary ridge, and associated with Müller microvilli. By immunofluorescence, Ringer's wash removed most of the diffuse IRBP, but not that coating the outer segments. IRBP-Alexa 647 bound to the cone outer segments and Müller villi region, and comparably less to rod outer segments. Co-incubation with unlabeled IRBP markedly reduced this binding; ovalbumin-Alexa 647 and Alexa 647 dye alone showed no binding. Our data suggest that the pericellular matrix of the cone outer segments and Müller microvilli provide specialized domains that facilitate IRBP's functions. Copyright © 2013 Elsevier Ltd. All rights reserved.

Biochemical Measurements of Free Opsin in Macular Degeneration Eyes: Examining the 11-CIS Retinal Deficiency Hypothesis of Delayed Dark Adaptation (An American Ophthalmological Society Thesis).

PubMed

Hanneken, Anne; Neikirk, Thomas; Johnson, Jennifer; Kono, Masahiro

2017-08-01

To test the hypothesis that delayed dark adaptation in patients with macular degeneration is due to an excess of free unliganded opsin (apo-opsin) and a deficiency of the visual chromophore, 11 -cis retinal, in rod outer segments. A total of 50 human autopsy eyes were harvested from donors with and without macular degeneration within 2-24 hrs. postmortem. Protocols were developed which permitted dark adaptation of normal human eyes after death and enucleation. Biochemical methods of purifying rod outer segments were optimized and the concentration of rhodopsin and apo-opsin was measured with UV-visible scanning spectroscopy. The presence of apo-opsin was calculated by measuring the difference in the rhodopsin absorption spectra before and after the addition of 11 -cis retinal. A total of 20 normal eyes and 16 eyes from donors with early, intermediate and advanced stages of macular degeneration were included in the final analysis. Dark adaptation was achieved by harvesting whole globes in low light, transferring into dark (light-proof) canisters and dissecting the globes using infrared light and image converters for visualization. Apo-opsin was readily detected in positive controls after the addition of 11 -cis retinal. Normal autopsy eyes showed no evidence of apo-opsin. Eyes with macular degeneration also showed no evidence of apo-opsin, regardless of the severity of disease. Methods have been developed to study dark adaptation in human autopsy eyes. Eyes with age-related macular degeneration do not show a deficiency of 11 -cis retinal or an excess of apo-opsin within rod outer segments.

Concentric retinitis pigmentosa: clinicopathologic correlations.

PubMed

Milam, A H; De Castro, E B; Smith, J E; Tang, W X; John, S K; Gorin, M B; Stone, E M; Aguirre, G D; Jacobson, S G

2001-10-01

Progressive concentric (centripetal) loss of vision is one pattern of visual field loss in retinitis pigmentosa. This study provides the first clinicopathologic correlations for this form of retinitis pigmentosa. A family with autosomal dominant concentric retinitis pigmentosa was examined clinically and with visual function tests. A post-mortem eye of an affected 94 year old family member was processed for histopathology and immunocytochemistry with retinal cell specific antibodies. Unrelated simplex/multiplex patients with concentric retinitis pigmentosa were also examined. Affected family members of the eye donor and patients from the other families had prominent peripheral pigmentary retinopathy with more normal appearing central retina, good visual acuity, concentric field loss, normal or near normal rod and cone sensitivity within the preserved visual field, and reduced rod and cone electroretinograms. The eye donor, at age 90, had good acuity and function in a central island. Grossly, the central region of the donor retina appeared thinned but otherwise normal, while the far periphery contained heavy bone spicule pigment. Microscopically the central retina showed photoreceptor outer segment shortening and some photoreceptor cell loss. The mid periphery had a sharp line of demarcation where more central photoreceptors were near normal except for very short outer segments and peripheral photoreceptors were absent. Rods and cones showed abrupt loss of outer segments and cell death at this interface. It is concluded that concentric retinitis pigmentosa is a rare but recognizable phenotype with slowly progressive photoreceptor death from the far periphery toward the central retina. The disease is retina-wide but shows regional variation in severity of degeneration; photoreceptor death is severe in the peripheral retina with an abrupt edge between viable and degenerate photoreceptors. Peripheral to central gradients of unknown retinal molecule(s) may be defective or modify photoreceptor degeneration in concentric retinitis pigmentosa.

Mfsd2a Is a Transporter for the Essential ω-3 Fatty Acid Docosahexaenoic Acid (DHA) in Eye and Is Important for Photoreceptor Cell Development*

PubMed Central

Wong, Bernice H.; Chan, Jia Pei; Cazenave-Gassiot, Amaury; Poh, Rebecca W.; Foo, Juat Chin; Galam, Dwight L. A.; Ghosh, Sujoy; Nguyen, Long N.; Barathi, Veluchamy A.; Yeo, Sia W.; Luu, Chi D.; Wenk, Markus R.; Silver, David L.

2016-01-01

Eye photoreceptor membrane discs in outer rod segments are highly enriched in the visual pigment rhodopsin and the ω-3 fatty acid docosahexaenoic acid (DHA). The eye acquires DHA from blood, but transporters for DHA uptake across the blood-retinal barrier or retinal pigment epithelium have not been identified. Mfsd2a is a newly described sodium-dependent lysophosphatidylcholine (LPC) symporter expressed at the blood-brain barrier that transports LPCs containing DHA and other long-chain fatty acids. LPC transport via Mfsd2a has been shown to be necessary for human brain growth. Here we demonstrate that Mfsd2a is highly expressed in retinal pigment epithelium in embryonic eye, before the development of photoreceptors, and is the primary site of Mfsd2a expression in the eye. Eyes from whole body Mfsd2a-deficient (KO) mice, but not endothelium-specific Mfsd2a-deficient mice, were DHA-deficient and had significantly reduced LPC/DHA transport in vivo. Fluorescein angiography indicated normal blood-retinal barrier function. Histological and electron microscopic analysis indicated that Mfsd2a KO mice exhibited a specific reduction in outer rod segment length, disorganized outer rod segment discs, and mislocalization of and reduction in rhodopsin early in postnatal development without loss of photoreceptors. Minor photoreceptor cell loss occurred in adult Mfsd2a KO mice, but electroretinography indicated visual function was normal. The developing eyes of Mfsd2a KO mice had activated microglia and up-regulation of lipogenic and cholesterogenic genes, likely adaptations to loss of LPC transport. These findings identify LPC transport via Mfsd2a as an important pathway for DHA uptake in eye and for development of photoreceptor membrane discs. PMID:27008858

Calcium and magnesium fluxes across the plasma membrane of the toad rod outer segment.

PubMed Central

Nakatani, K; Yau, K W

1988-01-01

1. Membrane current was recorded from an isolated, dark-adapted toad rod by sucking either its inner segment or outer segment into a tight-fitting glass pipette containing Ringer solution. The remainder of the cell was exposed to bath solution which could be changed rapidly. 2. In normal Ringer solution the current response of a cell to a saturating flash or step of light showed a small secondary rise at its initial peak. The profile of this secondary rise (i.e. amplitude and time course) was independent of both the intensity and the duration of illumination once the light response had reached a plateau level. 3. This secondary rise disappeared when external Na+ around the outer segment was replaced by Li+ or guanidinium, suggesting that it represented an electrogenic Na+-dependent Ca2+ efflux which was declining after the onset of light. 4. This Na+-Ca2+ exchange activity showed a roughly exponential decline, with a time constant of about 0.5 s. Exponential extrapolation of the exchange current to the time at half-height of the light response gave an initial amplitude of about 2 pA. Using La3+ as a blocker, we did not detect any steady exchange current after the initial exponential decline. 5. An intense flash superposed on a just-saturating steady background light failed to produce any incremental exchange current transient. 6. Our interpretation of the above results is that in darkness there are counterbalancing levels of Ca2+ influx (through the light-sensitive conductance) and efflux (through the Na+-Ca2+ exchange) across the plasma membrane of the rod outer segment. The exchange current transient at the onset of light merely represents the unidirectional Ca2+ efflux which becomes revealed as a result of the stoppage of the Ca2+ influx, rather than a de novo Ca2+ efflux triggered by light. 7. Consistent with this interpretation, a test light delivered soon after a saturating, conditioning light elicited little exchange current, which then gradually recovered to control value with a time course parallel to the restoration of the dark current. Conversely, when the dark current was increased above its physiological level by IBMX (isobutylmethylxanthine) the exchange current transient became larger than control.(ABSTRACT TRUNCATED AT 400 WORDS) Images Fig. 8 PMID:2457685

Ca sup 2+ binding capacity of cytoplasmic proteins from rod photoreceptors is mainly due to arrestin

DOE Office of Scientific and Technical Information (OSTI.GOV)

Huppertz, B.; Weyand, I.; Bauer, P.J.

1990-06-05

Arrestin (also called S-antigen or 48-kDa protein) binds to photoexcited and phosphorylated rhodopsin and, thereby, blocks competitively the activation of transducin. Using Ca{sup 2+} titration in the presence of the indicator arsenazo III and {sup 45}Ca{sup 2+} autoradiography, we show that arrestin is a Ca2(+)-binding protein. The Ca{sup 2+} binding capacity of arresting-containing protein extracts from bovine rod outer segments is about twice as high as that of arrestin-depleted extracts. The difference in the Ca{sup 2+} binding of arrestin-containing and arrestin-depleted protein extracts was attributed to arrestin. Both, these difference-measurements of protein extracts and the measurements of purified arrestin yieldmore » dissociation constants for the Ca{sup 2+} binding of arrestin between 2 and 4 microM. The titration curves are consistent with a molar ratio of one Ca{sup 2+} binding site per arrestin. No Ca{sup 2+} binding in the micromolar range was found in extracts containing mainly transducin and cGMP-phosphodiesterase. Since arrestin is one of the most abundant proteins in rod photoreceptors occurring presumably up to millimolar concentrations in rod outer segments, we suggest that aside from its function to prevent the activation of transducin, arrestin acts probably as an intracellular Ca{sup 2+} buffer.« less

THE ORGANOPHOSPHOROUS INSECTICIDE FENTHION DOES NOT AFFECT PHAGOCYTOSIS OF ROD OUTER SEGMENTS BY RETINAL PIGMENT EPITHELIUM CELLS IN CULTURE.

EPA Science Inventory

:
Exposure to the organophosphorous insecticide fenthion has been associated with retinal degeneration in occupational studies. It has also been associated with pigmentary changes of the retina. Because retinal degeneration and pigmentary changes may be due to dysfunction of t...

Development of an MRI biomarker sensitive to tetrameric visual arrestin 1 and its reduction via light-evoked translocation in vivo

PubMed Central

Berkowitz, Bruce A.; Gorgis, Jawan; Patel, Ankit; Baameur, Faiza; Gurevich, Vsevolod V.; Craft, Cheryl M.; Kefalov, Vladimir J.; Roberts, Robin

2015-01-01

Rod tetrameric arrestin 1 (tet-ARR1), stored in the outer nuclear layer/inner segments in the dark, modulates photoreceptor synaptic activity; light exposure stimulates a reduction via translocation to the outer segments for terminating G-protein coupled phototransduction signaling. Here, we test the hypothesis that intraretinal spin-lattice relaxation rate in the rotating frame (1/T1ρ), an endogenous MRI contrast mechanism, has high potential for evaluating rod tet-ARR1 and its reduction via translocation. Dark- and light-exposed mice (null for the ARR1 gene, overexpressing ARR1, diabetic, or wild type with or without treatment with Mn2+, a calcium channel probe) were studied using 1/T1ρ MRI. Immunohistochemistry and single-cell recordings of the retinas were also performed. In wild-type mice with or without treatment with Mn2+, 1/T1ρ of avascular outer retina (64% to 72% depth) was significantly (P < 0.05) greater in the dark than in the light; a significant (P < 0.05) but opposite pattern was noted in the inner retina (<50% depth). Light-evoked outer retina Δ1/T1ρ was absent in ARR1-null mice and supernormal in overexpressing mice. In diabetic mice, the outer retinal Δ1/T1ρ pattern suggested normal dark-to-light tet-ARR1 translocation and chromophore content, conclusions confirmed ex vivo. Light-stimulated Δ1/T1ρ in inner retina was linked to changes in blood volume. Our data support 1/T1ρ MRI for noninvasively assessing rod tet-ARR1 and its reduction via protein translocation, which can be combined with other metrics of retinal function in vivo.—Berkowitz, B. A., Gorgis, J., Patel, A., Baameur, F., Gurevich, V. V., Craft, C. M., Kefalov, V. J., Roberts, R. Development of an MRI biomarker sensitive to tetrameric visual arrestin 1 and its reduction via light-evoked translocation in vivo. PMID:25351983

Migration, Integration and Maturation of Photoreceptor Precursors Following Transplantation in the Mouse Retina

PubMed Central

Warre-Cornish, Katherine; Barber, Amanda C.; Sowden, Jane C.; Ali, Robin R.

2014-01-01

Retinal degeneration leading to loss of photoreceptors is a major cause of untreatable blindness. Recent research has yielded definitive evidence for restoration of vision following the transplantation of rod photoreceptors in murine models of blindness, while advances in stem cell biology have enabled the generation of transplantable photoreceptors from embryonic stem cells. Importantly, the amount of visual function restored is dependent upon the number of photoreceptors that migrate correctly into the recipient retina. The developmental stage of the donor cells is important for their ability to migrate; they must be immature photoreceptor precursors. Little is known about how and when donor cell migration, integration, and maturation occurs. Here, we have performed a comprehensive histological analysis of the 6-week period following rod transplantation in mice. Donor cells migrate predominately as single entities during the first week undergoing a stereotyped sequence of morphological changes in their translocation from the site of transplantation, through the interphotoreceptor matrix and into the recipient retina. This includes initial polarization toward the outer nuclear layer (ONL), followed by formation of an apical attachment and rudimentary segment during migration into the ONL. Strikingly, acquisition of a nuclear architecture typical of mature rods was accelerated compared with normal development and a feature of migrating cells. Once within the ONL, precursors formed synaptic-like structures and outer segments in accordance with normal maturation. The restoration of visual function mediated by transplanted photoreceptors correlated with the later expression of rod α-transducin, achieving maximal function by 5 weeks. PMID:24328605

Freeze-fracture studies of photoreceptor membranes: new observations bearing upon the distribution of cholesterol

PubMed Central

1983-01-01

We performed electron microscopy of replicas from freeze-fractured retinas exposed during or after fixation to the cholesterol-binding antibiotic, filipin. We observed characteristic filipin-induced perturbations throughout the disk and plasma membranes of retinal rod outer segments of various species. It is evident that a prolonged exposure to filipin in fixative enhances rather than reduces presumptive cholesterol detection in the vertebrate photoreceptor cell. In agreement with the pattern seen in our previous study (Andrews, L.D., and A. I. Cohen, 1979, J. Cell Biol., 81:215-228), filipin- binding in membranes exhibiting particle-free patches seemed largely confined to these patches. Favorably fractured photoreceptors exhibited marked filipin-binding in apical inner segment plasma membrane topologically confluent with and proximate to the outer segment plasma membrane, which was comparatively free of filipin binding. A possible boundary between these differing membrane domains was suggested in a number of replicas exhibiting lower filipin binding to the apical plasma membrane of the inner segment in the area surrounding the cilium. This area contains a structure (Andrews, L. D., 1982, Freeze- fracture studies of vertebrate photoreceptors, In Structure of the Eye, J. G. Hollyfield and E. Acosta Vidrio, editors, Elsevier/North-Holland, New York, 11-23) that resembles the active zones of the nerve terminals for the frog neuromuscular junction. These observations lead us to hypothesize that these structures may function to direct vesicle fusion to occur near them, in a domain of membrane more closely resembling outer than inner segment plasma membrane. The above evidence supports the views that (a) all disk membranes contain cholesterol, but the particle-free patches present in some disks trap cholesterol from contiguous particulate membrane regions; (b) contiguous inner and outer segment membranes may greatly differ in cholesterol content; and (c) the suggested higher cholesterol in the inner segment than in the outer segment plasma membrane may help direct newly inserted photopigment molecules to the outer segment. PMID:6411740

Kinetics and components of the flash photocurrent of isolated retinal rods of the larval salamander, Ambystoma tigrinum.

PubMed Central

Cobbs, W H; Pugh, E N

1987-01-01

1. Membrane currents initiated by intense, 20 microseconds flashes (photocurrents) were recorded from isolated salamander rods by combined extracellular suction electrodes and intracellular tight-seal electrodes either in current or voltage clamp mode. The magnitudes (mean +/- 2 S.E.M.) of the maximal photoresponses recorded by the suction and by the intracellular electrode respectively were 40 +/- 5 pA (n = 18) and 35 +/- 7 mV (n = 8) for current clamp at zero current; 43 +/- 9 pA and 66 +/- 13 (n = 11) pA for voltage clamp at the zero-current holding potential, -24 +/- 3 mV. 2. Photocurrents initiated by flashes isomerizing 0.1% or more of the outer segment's rhodopsin achieved a saturated velocity and were 95% complete in less than 50 ms. The effect of incrementing flash intensity above 0.1% isomerization can be described as a translation of the photocurrent along the time axis towards the origin. Within the interval 0-50 ms the latter two-thirds of the velocity-saturated photocurrent is well described as a single-exponential decay. The decay was much faster in voltage clamp (2.8 +/- 1.2 ms, n = 11) than in current clamp mode (17 +/- 5 ms, n = 17). 3. The initial third of the velocity-saturated photocurrent, occurring over the interval from the flash to the onset of exponential decay, followed about the same time course in current and voltage clamp. The time interval occupied by this initial 'latent' phase decreased with increasing flash intensity and attained an apparent minimum of about 7 ms in response to flashes isomerizing 10% or more of the rhodopsin at ca. 22 degrees C. 4. The hypothesis that the decay of outer segment light-sensitive membrane current is the same in current and voltage clamp was supported by an analysis of the difference between outer segment currents measured successively in the two recording modes. First, the tail of the difference current decayed exponentially with a time constant approximately equal to R x C, where R and C are independently estimated slope resistance and capacitance of the rod. Secondly, the integral of the difference current, when divided by outer segment capacitance, closely approximated the hyperpolarizing light response measured under current clamp. Thus, displacement current accounted for the difference between photocurrents measured in current and voltage clamp.(ABSTRACT TRUNCATED AT 400 WORDS) PMID:2832596

Retinal pigment epithelial dystrophy in Briard dogs.

PubMed

Lightfoot, R M; Cabral, L; Gooch, L; Bedford, P G; Boulton, M E

1996-01-01

The eyes of normal Briard dogs, Briards affected with inherited retinal pigment epithelial dystrophy (RPED) and a range of normal crossbred and beagle dogs were examined and the histopathology of RPED in the Briard was compared with the histopathological features of ageing in the normal canine retina. RPED was characterised by the accumulation of auto-fluorescent lipofuscin-like inclusions in the retinal pigment epithelium (RPE), which initially involved only non-pigmented RPE cells overlying the tapetum but subsequently spread to all pigmented RPE cells. Secondary neuro-retinal degeneration was characterised by a gradual loss of the outer nuclear layer and the subsequent atrophy and degeneration of the inner retina. The loss of primary photoreceptors in the peripheral retina was accompanied by the migration of photoreceptor nuclei and appeared to resemble severe changes due to ageing. Intra-vitreal radiolabelled leucine was used to examine the rate of turnover of the outer segments of the rods in some Briards, but no significant variations were found. The activity of acid phosphatase in RPE was assayed in vitro and showed comparable regional variations in Briard and crossbred dogs. The results suggest that RPED in the Briard is unlikely to be due either to an increased rate of turnover of rod outer segments (and thus an increased phagocytic load) or to a primary insufficiency of lysosomal enzyme.

Developing rods transplanted into the degenerating retina of Crx-knockout mice exhibit neural activity similar to native photoreceptors

PubMed Central

Homma, Kohei; Okamoto, Satoshi; Mandai, Michiko; Gotoh, Norimoto; Rajasimha, Harsha K.; Chang, Yi-Sheng; Chen, Shan; Li, Wei; Cogliati, Tiziana; Swaroop, Anand; Takahashi, Masayo

2013-01-01

Replacement of dysfunctional or dying photoreceptors offers a promising approach for retinal neurodegenerative diseases, including age-related macular degeneration and retinitis pigmentosa. Several studies have demonstrated the integration and differentiation of developing rod photoreceptors when transplanted in wild type or degenerating retina; however, the physiology and function of the donor cells are not adequately defined. Here, we describe the physiological properties of developing rod photoreceptors that are tagged with GFP driven by the promoter of rod differentiation factor, Nrl. GFP-tagged developing rods show Ca2+ responses and rectifier outward currents that are smaller than those observed in fully developed photoreceptors, suggesting their immature developmental state. These immature rods also exhibit hyperpolarization-activated current (Ih) induced by the activation of hyperpolarization-activated cyclic nucleotide-gated (HCN) channels. When transplanted into the subretinal space of wild type or retinal degeneration mice, GFP-tagged developing rods can integrate into the photoreceptor outer nuclear layer in wild-type mouse retina, and exhibit Ca2+ responses and membrane current comparable to native rod photoreceptors. A proportion of grafted rods develop rhodopsin-positive outer segment-like structures within two weeks after transplantation into the retina of Crx-knockout mice, and produce rectifier outward current and Ih upon membrane depolarization and hyperpolarization. GFP-positive rods derived from induced pluripotent stem (iPS) cells also display similar membrane current Ih as native developing rod photoreceptors, express rod-specific phototransduction genes, and HCN-1 channels. We conclude that Nrl-promoter driven GFP-tagged donor photoreceptors exhibit physiological characteristics of rods and that iPS cell-derived rods in vitro may provide a renewable source for cell replacement therapy. PMID:23495178

Role of recoverin in rod photoreceptor light adaptation.

PubMed

Morshedian, Ala; Woodruff, Michael L; Fain, Gordon L

2018-04-15

Recoverin is a small molecular-weight, calcium-binding protein in rod outer segments that can modulate the rate of rhodopsin phosphorylation. We describe two additional and perhaps more important functions during photoreceptor light adaptation. Recoverin influences the rate of change of adaptation. In wild-type rods, sensitivity and response integration time adapt with similar time constants of 150-200 ms. In Rv-/- rods lacking recoverin, sensitivity declines faster and integration time is already shorter and not significantly altered. During steady light exposure, rod circulating current slowly increases during a time course of tens of seconds, gradually extending the operating range of the rod. In Rv-/- rods, this mechanism is deleted, steady-state currents are already larger and rods saturate at brighter intensities. We propose that recoverin modulates spontaneous and light-activated phophodiesterase-6, the phototransduction effector enzyme, to increase sensitivity in dim light but improve responsiveness to change in brighter illumination. Recoverin is a small molecular-weight, calcium-binding protein in rod outer segments that binds to G-protein receptor kinase 1 and can alter the rate of rhodopsin phosphorylation. A change in phosphorylation should change the lifetime of light-activated rhodopsin and the gain of phototransduction, but deletion of recoverin has little effect on the sensitivity of rods either in the dark or in dim-to-moderate background light. We describe two additional functions perhaps of greater physiological significance. (i) When the ambient intensity increases, sensitivity and integration time decrease in wild-type (WT) rods with similar time constants of 150-200 ms. Recoverin is part of the mechanism controlling this process because, in Rv-/- rods lacking recoverin, sensitivity declines more rapidly and integration time is already shorter and not further altered. (ii) During steady light exposure, WT rod circulating current slowly increases during a time course of tens of seconds, gradually extending the operating range of the rod. In Rv-/- rods, this mechanism is also deleted, steady-state currents are already larger and rods saturate at brighter intensities. We argue that neither (i) nor (ii) can be caused by modulation of rhodopsin phosphorylation but may instead be produced by direct modulation of phophodiesterase-6 (PDE6), the phototransduction effector enzyme. We propose that recoverin in dark-adapted rods keeps the integration time long and the spontaneous PDE6 rate relatively high to improve sensitivity. In background light, the integration time is decreased to facilitate detection of change and motion and the spontaneous PDE6 rate decreases to augment the rod working range. © 2018 The Authors. The Journal of Physiology © 2018 The Physiological Society.

Distinct functions for IFT140 and IFT20 in opsin transport.

PubMed Central

Crouse, Jacquelin A.; Lopes, Vanda S.; SanAgustin, Jovenal T.; Keady, Brian T.; Williams, David S.; Pazour, Gregory J.

2014-01-01

In the vertebrate retina, light is detected by the outer segments of photoreceptor rods and cones, which are highly modified cilia. Like other cilia, outer segments have no protein synthetic capacity and depend on proteins made in the cell body for their formation and maintenance. The mechanism of transport into the outer segment is not fully understood but intraflagellar transport (IFT) is thought to be a major mechanism for moving protein from the cell body into the cilium. In the case of photoreceptor cells, the high density of receptors and the disk turnover that occurs daily necessitates much higher rates of transport than would be required in other cilia. In this work, we show that the IFT complex A protein IFT140 is required for development and maintenance of outer segments. In earlier work we found that acute deletion of Ift20 caused opsin to accumulate at the Golgi complex. In this work we find that acute deletion of Ift140 does not cause opsin to accumulate at the Golgi complex but rather it accumulates in the plasma membrane of the inner segments. This work is strong support of a model of opsin transport where IFT20 is involved in the movement from the Golgi complex to the base of the cilium. Then, once at the base, the opsin is carried through the connecting cilium by an IFT complex that includes IFT140. PMID:24619649

Mfsd2a Is a Transporter for the Essential ω-3 Fatty Acid Docosahexaenoic Acid (DHA) in Eye and Is Important for Photoreceptor Cell Development.

PubMed

Wong, Bernice H; Chan, Jia Pei; Cazenave-Gassiot, Amaury; Poh, Rebecca W; Foo, Juat Chin; Galam, Dwight L A; Ghosh, Sujoy; Nguyen, Long N; Barathi, Veluchamy A; Yeo, Sia W; Luu, Chi D; Wenk, Markus R; Silver, David L

2016-05-13

Eye photoreceptor membrane discs in outer rod segments are highly enriched in the visual pigment rhodopsin and the ω-3 fatty acid docosahexaenoic acid (DHA). The eye acquires DHA from blood, but transporters for DHA uptake across the blood-retinal barrier or retinal pigment epithelium have not been identified. Mfsd2a is a newly described sodium-dependent lysophosphatidylcholine (LPC) symporter expressed at the blood-brain barrier that transports LPCs containing DHA and other long-chain fatty acids. LPC transport via Mfsd2a has been shown to be necessary for human brain growth. Here we demonstrate that Mfsd2a is highly expressed in retinal pigment epithelium in embryonic eye, before the development of photoreceptors, and is the primary site of Mfsd2a expression in the eye. Eyes from whole body Mfsd2a-deficient (KO) mice, but not endothelium-specific Mfsd2a-deficient mice, were DHA-deficient and had significantly reduced LPC/DHA transport in vivo Fluorescein angiography indicated normal blood-retinal barrier function. Histological and electron microscopic analysis indicated that Mfsd2a KO mice exhibited a specific reduction in outer rod segment length, disorganized outer rod segment discs, and mislocalization of and reduction in rhodopsin early in postnatal development without loss of photoreceptors. Minor photoreceptor cell loss occurred in adult Mfsd2a KO mice, but electroretinography indicated visual function was normal. The developing eyes of Mfsd2a KO mice had activated microglia and up-regulation of lipogenic and cholesterogenic genes, likely adaptations to loss of LPC transport. These findings identify LPC transport via Mfsd2a as an important pathway for DHA uptake in eye and for development of photoreceptor membrane discs. © 2016 by The American Society for Biochemistry and Molecular Biology, Inc.

Identification of endogenous fluorophores in the photoreceptors using autofluorescence spectroscopy

NASA Astrophysics Data System (ADS)

Zhao, Lingling; Qu, Junle; Niu, Hanben

2007-11-01

In this paper, we present our investigation on the identification of endogenous fluorophores in photoreceptors using autofluorescence spectroscopy, which is performed with an inverted laser scanning confocal microscope equipped with an Argon ion laser and a GreNe laser. In our experiments, individual cones and rods are clearly resolved even in freshly prepared retina samples, without slicing or labeling. The experiment results show that autofluorescence spectrum of the photoreceptors has three peaks approximately at 525nm, 585nm and 665nm. Furthermore, the brightest autofluorescence originates from the photoreceptor outer segments. We can, therefore, come to a conclusion that the peaks at 525nm, 585nm are corresponding to FAD and A2-PE, respectively, which are distributed in the photoreceptor outer segments.

HYPERAUTOFLUORESCENT RING IN AUTOIMMUNE RETINOPATHY

PubMed Central

LIMA, LUIZ H.; GREENBERG, JONATHAN P.; GREENSTEIN, VIVIENNE C.; SMITH, R. THEODORE; SALLUM, JULIANA M. F.; THIRKILL, CHARLES; YANNUZZI, LAWRENCE A.; TSANG, STEPHEN H.

2015-01-01

Purpose To report the presence of a hyperautofluorescent ring and corresponding spectral-domain optical coherence tomography (SD-OCT) features seen in patients with autoimmune retinopathy. Methods All eyes were evaluated by funduscopic examination, full-fleld electroretinography, fundus autofluorescence, and SD-OCT. Further confirmation of the diagnosis was obtained with immunoblot and immunohistochemistry testing of the patient’s serum. Humphrey visual fields and microperimetry were also performed. Results Funduscopic examination showed atrophic retinal pigment epithelium (RPE) associated with retinal artery narrowing but without pigment deposits. The scotopic and photopic full-field electroretinograms were nondetectable in three patients and showed a cone–rod pattern of dysfunction in one patient. Fundus autofluorescence revealed a hyperautofluorescent ring in the parafoveal region, and the corresponding SD-OCT demonstrated loss of the photoreceptor inner segment–outer segment junction with thinning of the outer nuclear layer from the region of the hyperautofluorescent ring toward the retinal periphery. The retinal layers were generally intact within the hyperautofluorescent ring, although the inner segment–outer segment junction was disrupted, and the outer nuclear layer and photoreceptor outer segment layer were thinned. Conclusion This case series revealed the structure of the hyperautofluorescent ring in autoimmune retinopathy using SD-OCT. Fundus autofluorescence and SD-OCT may aid in the diagnosis of autoimmune retinopathy and may serve as a tool to monitor its progression. PMID:22218149

A photoreceptor calcium binding protein is recognized by autoantibodies obtained from patients with cancer-associated retinopathy

PubMed Central

1991-01-01

Cancer-associated retinopathy (CAR), a paraneoplastic syndrome, is characterized by the degeneration of retinal photoreceptors under conditions where the tumor and its metastases have not invaded the eye. The retinopathy often is apparent before the diagnosis of cancer and may be associated with autoantibodies that react with specific sites in the retina. We have examined the sera from patients with CAR to further characterize the retinal antigen. Western blot analysis of human retinal proteins reveals a prominent band at 26 kD that is labeled by the CAR antisera. Antibodies to the 26-kD protein were affinity- purified from complex CAR antisera and used for EM-immunocytochemical localization of the protein to the nuclei, inner and outer segments of both rod and cone cells. Other antibodies obtained from the CAR sera did not label photoreceptors. Using the affinity-purified antibodies for detection, the 26-kD protein, designated p26, was purified to homogeneity from the outer segments of bovine rod photoreceptor cells by Phenyl-Sepharose and ion exchange chromatography. Partial amino acid sequence of p26 was determined by gas phase Edman degradation and revealed extensive homology with a cone-specific protein, visinin. Based upon structural relatedness, both the p26 rod protein and visinin are members of the calmodulin family and contain calcium binding domains of the E-F hand structure. PMID:1999465

Effect of hydroxylamine on photon-like events during dark adaptation in toad rod photoreceptors.

PubMed Central

Leibrock, C S; Lamb, T D

1997-01-01

1. The suction pipette technique was used to investigate the recovery of toad rod photoreceptors following small bleaches of 0.2-3% of the rhodopsin. 2. The reduction in sensitivity and the increase in noise elicited by bleaches were measured, and from these measurements the underlying rate of occurrence of photon-like events was calculated as a function of time after the bleach. 3. Exposure to hydroxylamine solution was used to hasten the decomposition of the metarhodopsin photoproducts. The outer segment was exposed to 110 mM hydroxylamine in a low-Ca2+ Ringer solution for a period of 10-50 s beginning 10-17 min after the bleaching exposure. 4. By the time of the hydroxylamine exposure, the flash sensitivity and response kinetics had returned almost to normal, and were not significantly altered by the exposure. 5. Following hydroxylamine exposure, the rate of spontaneous photon-like events in the rods declined rapidly to near pre-bleach levels. 6. We conclude that hydroxylamine reduces the rate of occurrence of photon-like events induced by a bleach, and we postulate that this reduction results from the removal of metarhodopsin (most likely metarhodopsin II) from the outer segment. 7. Our results are consistent with a model in which photon-like events result from reversal of the reactions (phosphorylation and capping by arrestin) that lead to inactivation of the activated form of rhodopsin, Rh*. PMID:9174997

Impairment of extramitochondrial oxidative phosphorylation in mouse rod outer segments by blue light irradiation.

PubMed

Calzia, Daniela; Panfoli, Isabella; Heinig, Nora; Schumann, Ulrike; Ader, Marius; Traverso, Carlo Enrico; Funk, Richard H W; Roehlecke, Cora

2016-06-01

Exposure to short wavelength light causes increased reactive oxygen intermediates production in the outer retina, particularly in the rod Outer Segments (OS). Consistently, the OS were shown to conduct aerobic ATP production through the ectopic expression of the electron transfer chain complexes I-IV and F1Fo-ATP synthase. These facts prompted us to verify if the oxidative phosphorylation in the OS is implied in the oxidative damage of the blue-light (BL) treated OS, in an organotypic model of mouse retina. Whole mouse eyeball cultures were treated with short wavelength BL (peak at 405 nm, output power 1 mW/cm(2)) for 6 h. Immunogold transmission electron microscopy confirmed the expression of Complex I and F1Fo-ATP synthase in the OS. In situ histochemical assays on unfixed sections showed impairment of respiratory Complexes I and II after BL exposure, both in the OS and IS, utilized as a control. Basal O2 consumption and ATP synthesis were impaired in the OS purified from blue-light irradiated eyeball cultures. Electron transfer capacity between Complex I and II as well as activity of Complexes I and II was decreased in blue-light irradiated purified OS. The severe malfunctioning of the OS aerobic respiratory capacity after 6 h BL treatment may be the consequence of a self-induced damage. BL exposure would cause an initial over-functioning of both the phototransduction and respiratory chain, with reactive oxygen species production. In a self-renewal vicious cycle, membrane and protein oxidative damage, proton leakage and uncoupling, would impair redox chains, perpetuating the damage and causing hypo-metabolism with eventual apoptosis of the rod. Data may shed new light on the rod-driven retinopathies such as Age Related Macular Degeneration, of which blue-light irradiated retina represents a model. Copyright © 2016 Elsevier B.V. and Société Française de Biochimie et Biologie Moléculaire (SFBBM). All rights reserved.

Light-Dependent Redistribution of Arrestin in Vertebrate Rods Is an Energy-Independent Process Governed by Protein-Protein Interactions

PubMed Central

Nair, K. Saidas; Hanson, Susan M.; Mendez, Ana; Gurevich, Eugenia V.; Kennedy, Matthew J.; Shestopalov, Valery I.; Vishnivetskiy, Sergey A.; Chen, Jeannie; Hurley, James B.; Gurevich, Vsevolod V.; Slepak, Vladlen Z.

2009-01-01

Summary In rod photoreceptors, arrestin localizes to the outer segment (OS) in the light and to the inner segment (IS) in the dark. Here, we demonstrate that redistribution of arrestin between these compartments can proceed in ATP-depleted photoreceptors. Translocation of transducin from the IS to the OS also does not require energy, but depletion of ATP or GTP inhibits its reverse movement. A sustained presence of activated rhodopsin is required for sequestering arrestin in the OS, and the rate of arrestin relocalization to the OS is determined by the amount and the phosphorylation status of photolyzed rhodopsin. Interaction of arrestin with microtubules is increased in the dark. Mutations that enhance arrestin-microtubule binding attenuate arrestin translocation to the OS. These results indicate that the distribution of arrestin in rods is controlled by its dynamic interactions with rhodopsin in the OS and microtubules in the IS and that its movement occurs by simple diffusion. PMID:15944125

Retinal Degeneration in a Rodent Model of Smith-Lemli-Opitz Syndrome

PubMed Central

Fliesler, Steven J.; Peachey, Neal S.; Richards, Michael J.; Nagel, Barbara A.; Vaughan, Dana K.

2010-01-01

Objective To assess the electrophysiologic, histologic, and biochemical features of an animal model of Smith-Lemli-Opitz syndrome (SLOS). Methods Sprague-Dawley rats were treated with AY9944, a selective inhibitor of 3β-hydroxysterol-Δ7-reductase (the affected enzyme in SLOS). Dark- and light-adapted electroretinograms were obtained from treated and control animals. From each animal, 1 retina was analyzed by microscopy, and the contralateral retina plus serum samples were analyzed for sterol composition. The main outcome measures were rod and cone electroretinographic amplitudes and implicit times, outer nuclear layer (ONL) thickness, rod outer segment length, pyknotic ONL nucleus counts, and the 7-dehydrocholesterol/ cholesterol mole ratio in the retina and serum. Results By 10 weeks’ postnatal age, rod and cone electroretinographic wave amplitudes in AY9944-treated animals were significantly reduced and implicit times were significantly increased relative to controls. Maximal rod photoresponse and gain values were reduced approximately 2-fold in treated animals relative to controls. The ONL thickness and average rod outer segment length were reduced by approximately 18% and 33%, respectively, and ONL pyknotic nucleus counts were approximately 4.5-fold greater in treated animals relative to controls. The retinal pigment epithelium of treated animals contained massive amounts of membranous/lipid inclusions not routinely observed in controls. The 7-dehydrocholesterol/cholesterol mole ratios in treated retinas and serum samples were approximately 5:1 and 9:1, respectively, whereas the ratios in control tissues were essentially zero. Conclusions This rodent model exhibits the key biochemical hallmarks associated with SLOS and displays electrophysiologic deficits comparable to or greater than those observed in the human disease. Clinical Relevance These results predict retinal degeneration in patients with SLOS, particularly those with the more severe (type II) form of the disease, and may be more broadly relevant to other inborn errors of cholesterol biosynthesis. This animal model may also be of use in evaluating therapeutic treatments for SLOS and in understanding the slow phototransduction kinetics observed in patients with SLOS. PMID:15302661

Protein sorting, targeting and trafficking in photoreceptor cells

PubMed Central

Pearring, Jillian N.; Salinas, Raquel Y.; Baker, Sheila A.; Arshavsky, Vadim Y.

2013-01-01

Vision is the most fundamental of our senses initiated when photons are absorbed by the rod and cone photoreceptor neurons of the retina. At the distal end of each photoreceptor resides a light-sensing organelle, called the outer segment, which is a modified primary cilium highly enriched with proteins involved in visual signal transduction. At the proximal end, each photoreceptor has a synaptic terminal, which connects this cell to the downstream neurons for further processing of the visual information. Understanding the mechanisms involved in creating and maintaining functional compartmentalization of photoreceptor cells remains among the most fascinating topics in ocular cell biology. This review will discuss how photoreceptor compartmentalization is supported by protein sorting, targeting and trafficking, with an emphasis on the best-studied cases of outer segment-resident proteins. PMID:23562855

A distance measurement between specific sites on the cytoplasmic surface of bovine rhodopsin in rod outer segment disk membranes.

PubMed

Albert, A D; Watts, A; Spooner, P; Groebner, G; Young, J; Yeagle, P L

1997-08-14

Structural information on mammalian integral membrane proteins is scarce. As part of work on an alternative approach to the structure of bovine rhodopsin, a method was devised to obtain an intramolecular distance between two specific sites on rhodopsin while in the rod outer segment disk membrane. In this report, the distance between the rhodopsin kinase phosphorylation site(s) on the carboxyl terminal and the top of the third transmembrane helix was measured on native rhodopsin. Rhodopsin was labeled with a nuclear spin label (31P) by limited phosphorylation with rhodopsin kinase. Major phosphorylation occurs at serines 343 and 338 on the carboxyl terminal. The phosphorylated rhodopsin was then specifically labeled on cysteine 140 with an electron spin label. Magic angle spinning 31P-nuclear magnetic resonance revealed the resonance arising from the phosphorylated protein. The enhancement of the transverse relaxation of this resonance by the paramagnetic spin label was observed. The strength of this perturbation was used to determine the through-space distance between the phosphorylation site(s) and the spin label position. A distance of 18 +/- 3 A was obtained.

Bicarbonate Modulates Photoreceptor Guanylate Cyclase (ROS-GC) Catalytic Activity*

PubMed Central

Duda, Teresa; Wen, Xiao-Hong; Isayama, Tomoki; Sharma, Rameshwar K.; Makino, Clint L.

2015-01-01

By generating the second messenger cGMP in retinal rods and cones, ROS-GC plays a central role in visual transduction. Guanylate cyclase-activating proteins (GCAPs) link cGMP synthesis to the light-induced fall in [Ca2+]i to help set absolute sensitivity and assure prompt recovery of the response to light. The present report discloses a surprising feature of this system: ROS-GC is a sensor of bicarbonate. Recombinant ROS-GCs synthesized cGMP from GTP at faster rates in the presence of bicarbonate with an ED50 of 27 mm for ROS-GC1 and 39 mm for ROS-GC2. The effect required neither Ca2+ nor use of the GCAPs domains; however, stimulation of ROS-GC1 was more powerful in the presence of GCAP1 or GCAP2 at low [Ca2+]. When applied to retinal photoreceptors, bicarbonate enhanced the circulating current, decreased sensitivity to flashes, and accelerated flash response kinetics. Bicarbonate was effective when applied either to the outer or inner segment of red-sensitive cones. In contrast, bicarbonate exerted an effect when applied to the inner segment of rods but had little efficacy when applied to the outer segment. The findings define a new regulatory mechanism of the ROS-GC system that affects visual transduction and is likely to affect the course of retinal diseases caused by cGMP toxicity. PMID:25767116

Pipe gripper

DOEpatents

Moyers, S.M.

1975-12-16

A device for gripping the exterior surface of a pipe or rod is described which has a plurality of wedges, each having a concave face which engages the outer surface of the pipe and each having a smooth face opposing the concave face. The wedges are seated on and their grooved concave faces are maintained in circular alignment by tapered axial segments of an opening extending through a wedge-seating member. The wedges are allowed to slide across the tapered axial segments so that such a sliding movement acts to vary the diameter of the circular alignment.

The retinal morphology and retinal histochemistry of a twilight fish Corydoras paleatus (J.).

PubMed

Yew, D T; Woo, H H

1976-01-01

1. The retinas of Corydoras paleatus were studied by histology (HE) and histochemistry (PAS and Nucleic acid). 2. Three types of visual cells were observed, namely rod, single cone and twin cone. All of them are PAS positive. 3. The histochemical PAS pattern of these visual cells differs from those species which are not of a twilight habitat. 4. Significant amount of RNA were not detected in the inner segments of visual cells in this species indicating a possible slow renewal of outer segments.

Highly efficient retinal metabolism in cones

PubMed Central

Miyazono, Sadaharu; Shimauchi-Matsukawa, Yoshie; Tachibanaki, Shuji; Kawamura, Satoru

2008-01-01

After bleaching of visual pigment in vertebrate photoreceptors, all-trans retinal is reduced to all-trans retinol by retinol dehydrogenases (RDHs). We investigated this reaction in purified carp rods and cones, and we found that the reducing activity toward all-trans retinal in the outer segment (OS) of cones is >30 times higher than that of rods. The high activity of RDHs was attributed to high content of RDH8 in cones. In the inner segment (IS) in both rods and cones, RDH8L2 and RDH13 were found to be the major enzymes among RDH family proteins. We further found a previously undescribed and effective pathway to convert 11-cis retinol to 11-cis retinal in cones: this oxidative conversion did not require NADP+ and instead was coupled with reduction of all-trans retinal to all-trans retinol. The activity was >50 times effective than the oxidizing activity of RDHs that require NADP+. These highly effective reactions of removal of all-trans retinal by RDH8 and production of 11-cis retinal by the coupling reaction are probably the underlying mechanisms that ensure effective visual pigment regeneration in cones that function under much brighter light conditions than rods. PMID:18836074

Differential distribution of proteins and lipids in detergent-resistant and detergent-soluble domains in rod outer segment plasma membranes and disks.

PubMed

Elliott, Michael H; Nash, Zack A; Takemori, Nobuaki; Fliesler, Steven J; McClellan, Mark E; Naash, Muna I

2008-01-01

Membrane heterogeneity plays a significant role in regulating signal transduction and other cellular activities. We examined the protein and lipid components associated with the detergent-resistant membrane (DRM) fractions from retinal rod outer segment (ROS) disk and plasma membrane-enriched preparations. Proteomics and correlative western blot analysis revealed the presence of alpha and beta subunits of the rod cGMP-gated ion channel and glucose transporter type 1, among other proteins. The glucose transporter was present exclusively in ROS plasma membrane (not disks) and was highly enriched in DRMs, as was the cGMP-gated channel beta-subunit. In contrast, the majority of rod opsin and ATP-binding cassette transporter A4 was localized to detergent-soluble domains in disks. As expected, the cholesterol : fatty acid mole ratio was higher in DRMs than in the corresponding parent membranes (disk and plasma membranes, respectively) and was also higher in disks compared to plasma membranes. Furthermore, the ratio of saturated : polyunsaturated fatty acids was also higher in DRMs compared to their respective parent membranes (disk and plasma membranes). These results confirm that DRMs prepared from both disks and plasma membranes are enriched in cholesterol and in saturated fatty acids compared to their parent membranes. The dominant fatty acids in DRMs were 16 : 0 and 18 : 0; 22 : 6n3 and 18 : 1 levels were threefold higher and twofold lower, respectively, in disk-derived DRMs compared to plasma membrane-derived DRMs. We estimate, based on fatty acid recovery that DRMs account for only approximately 8% of disks and approximately 12% of ROS plasma membrane.

Arrestin-rhodopsin binding stoichiometry in isolated rod outer segment membranes depends on the percentage of activated receptors.

PubMed

Sommer, Martha E; Hofmann, Klaus Peter; Heck, Martin

2011-03-04

In the rod cell of the retina, arrestin is responsible for blocking signaling of the G-protein-coupled receptor rhodopsin. The general visual signal transduction model implies that arrestin must be able to interact with a single light-activated, phosphorylated rhodopsin molecule (Rho*P), as would be generated at physiologically relevant low light levels. However, the elongated bi-lobed structure of arrestin suggests that it might be able to accommodate two rhodopsin molecules. In this study, we directly addressed the question of binding stoichiometry by quantifying arrestin binding to Rho*P in isolated rod outer segment membranes. We manipulated the "photoactivation density," i.e. the percentage of active receptors in the membrane, with the use of a light flash or by partially regenerating membranes containing phosphorylated opsin with 11-cis-retinal. Curiously, we found that the apparent arrestin-Rho*P binding stoichiometry was linearly dependent on the photoactivation density, with one-to-one binding at low photoactivation density and one-to-two binding at high photoactivation density. We also observed that, irrespective of the photoactivation density, a single arrestin molecule was able to stabilize the active metarhodopsin II conformation of only a single Rho*P. We hypothesize that, although arrestin requires at least a single Rho*P to bind the membrane, a single arrestin can actually interact with a pair of receptors. The ability of arrestin to interact with heterogeneous receptor pairs composed of two different photo-intermediate states would be well suited to the rod cell, which functions at low light intensity but is routinely exposed to several orders of magnitude more light.

Peripherin-2 couples rhodopsin to the CNG channel in outer segments of rod photoreceptors.

PubMed

Becirovic, Elvir; Nguyen, O N Phuong; Paparizos, Christos; Butz, Elisabeth S; Stern-Schneider, Gabi; Wolfrum, Uwe; Hauck, Stefanie M; Ueffing, Marius; Wahl-Schott, Christian; Michalakis, Stylianos; Biel, Martin

2014-11-15

Outer segments (OSs) of rod photoreceptors are cellular compartments specialized in the conversion of light into electrical signals. This process relies on the light-triggered change in the intracellular levels of cyclic guanosine monophosphate, which in turn controls the activity of cyclic nucleotide-gated (CNG) channels in the rod OS plasma membrane. The rod CNG channel is a macromolecular complex that in its core harbors the ion-conducting CNGA1 and CNGB1a subunits. To identify additional proteins of the complex that interact with the CNGB1a core subunit, we applied affinity purification of mouse retinal proteins followed by mass spectrometry. In combination with in vitro and in vivo co-immunoprecipitation and fluorescence resonance energy transfer (FRET), we found that the tetraspanin peripherin-2 links CNGB1a to the light-detector rhodopsin. Using immunoelectron microscopy, we found that this peripherin-2/rhodopsin/CNG channel complex localizes to the contact region between the disk rims and the plasma membrane. FRET measurements revealed that the fourth transmembrane domain (TM4) of peripherin-2 is required for the interaction with rhodopsin. Quantitatively, the binding affinity of the peripherin-2/rhodopsin interaction was in a similar range as that observed for rhodopsin dimers. Finally, we demonstrate that the p.G266D retinitis pigmentosa mutation found within TM4 selectively abolishes the binding of peripherin-2 to rhodopsin. This finding suggests that the specific disruption of the rhodopsin/peripherin-2 interaction in the p.G266D mutant might contribute to the pathophysiology in affected persons. © The Author 2014. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Three-dimensional organization of nascent rod outer segment disk membranes.

PubMed

Volland, Stefanie; Hughes, Louise C; Kong, Christina; Burgess, Barry L; Linberg, Kenneth A; Luna, Gabriel; Zhou, Z Hong; Fisher, Steven K; Williams, David S

2015-12-01

The vertebrate photoreceptor cell contains an elaborate cilium that includes a stack of phototransductive membrane disks. The disk membranes are continually renewed, but how new disks are formed remains poorly understood. Here we used electron microscope tomography to obtain 3D visualization of the nascent disks of rod photoreceptors in three mammalian species, to gain insight into the process of disk morphogenesis. We observed that nascent disks are invariably continuous with the ciliary plasma membrane, although, owing to partial enclosure, they can appear to be internal in 2D profiles. Tomographic analyses of the basal-most region of the outer segment show changes in shape of the ciliary plasma membrane indicating an invagination, which is likely a first step in disk formation. The invagination flattens to create the proximal surface of an evaginating lamella, as well as membrane protrusions that extend between adjacent lamellae, thereby initiating a disk rim. Immediately distal to this initiation site, lamellae of increasing diameter are evident, indicating growth outward from the cilium. In agreement with a previous model, our data indicate that mature disks are formed once lamellae reach full diameter, and the growth of a rim encloses the space between adjacent surfaces of two lamellae. This study provides 3D data of nascent and mature rod photoreceptor disk membranes at unprecedented z-axis depth and resolution, and provides a basis for addressing fundamental questions, ranging from protein sorting in the photoreceptor cilium to photoreceptor electrophysiology.

Photoreceptor Cell Death, Proliferation and Formation of Hybrid Rod/S-Cone Photoreceptors in the Degenerating STK38L Mutant Retina

PubMed Central

Berta, Ágnes I.; Boesze-Battaglia, Kathleen; Genini, Sem; Goldstein, Orly; O'Brien, Paul J.; Szél, Ágoston; Acland, Gregory M.; Beltran, William A.; Aguirre, Gustavo D.

2011-01-01

A homozygous mutation in STK38L in dogs impairs the late phase of photoreceptor development, and is followed by photoreceptor cell death (TUNEL) and proliferation (PCNA, PHH3) events that occur independently in different cells between 7–14 weeks of age. During this period, the outer nuclear layer (ONL) cell number is unchanged. The dividing cells are of photoreceptor origin, have rod opsin labeling, and do not label with markers specific for macrophages/microglia (CD18) or Müller cells (glutamine synthetase, PAX6). Nestin labeling is absent from the ONL although it labels the peripheral retina and ciliary marginal zone equally in normals and mutants. Cell proliferation is associated with increased cyclin A1 and LATS1 mRNA expression, but CRX protein expression is unchanged. Coincident with photoreceptor proliferation is a change in the photoreceptor population. Prior to cell death the photoreceptor mosaic is composed of L/M- and S-cones, and rods. After proliferation, both cone types remain, but the majority of rods are now hybrid photoreceptors that express rod opsin and, to a lesser extent, cone S-opsin, and lack NR2E3 expression. The hybrid photoreceptors renew their outer segments diffusely, a characteristic of cones. The results indicate the capacity for terminally differentiated, albeit mutant, photoreceptors to divide with mutations in this novel retinal degeneration gene. PMID:21980341

Lipofuscin and N-Retinylidene-N-Retinylethanolamine (A2E) Accumulate in Retinal Pigment Epithelium in Absence of Light Exposure

PubMed Central

Boyer, Nicholas P.; Higbee, Daniel; Currin, Mark B.; Blakeley, Lorie R.; Chen, Chunhe; Ablonczy, Zsolt; Crouch, Rosalie K.; Koutalos, Yiannis

2012-01-01

The age-dependent accumulation of lipofuscin in the retinal pigment epithelium (RPE) has been associated with the development of retinal diseases, particularly age-related macular degeneration and Stargardt disease. A major component of lipofuscin is the bis-retinoid N-retinylidene-N-retinylethanolamine (A2E). The current model for the formation of A2E requires photoactivation of rhodopsin and subsequent release of all-trans-retinal. To understand the role of light exposure in the accumulation of lipofuscin and A2E, we analyzed RPEs and isolated rod photoreceptors from mice of different ages and strains, reared either in darkness or cyclic light. Lipofuscin levels were determined by fluorescence imaging, whereas A2E levels were quantified by HPLC and UV-visible absorption spectroscopy. The identity of A2E was confirmed by tandem mass spectrometry. Lipofuscin and A2E levels in the RPE increased with age and more so in the Stargardt model Abca4−/− than in the wild type strains 129/sv and C57Bl/6. For each strain, the levels of lipofuscin precursor fluorophores in dark-adapted rods and the levels and rates of increase of RPE lipofuscin and A2E were not different between dark-reared and cyclic light-reared animals. Both 11-cis- and all-trans-retinal generated lipofuscin-like fluorophores when added to metabolically compromised rod outer segments; however, it was only 11-cis-retinal that generated such fluorophores when added to metabolically intact rods. The results suggest that lipofuscin originates from the free 11-cis-retinal that is continuously supplied to the rod for rhodopsin regeneration and outer segment renewal. The physiological role of Abca4 may include the translocation of 11-cis-retinal complexes across the disk membrane. PMID:22570475

Progressive Reduction of its Expression in Rods Reveals Two Pools of Arrestin-1 in the Outer Segment with Different Roles in Photoresponse Recovery

PubMed Central

Cleghorn, Whitney M.; Tsakem, Elviche L.; Song, Xiufeng; Vishnivetskiy, Sergey A.; Seo, Jungwon; Chen, Jeannie; Gurevich, Eugenia V.; Gurevich, Vsevolod V.

2011-01-01

Light-induced rhodopsin signaling is turned off with sub-second kinetics by rhodopsin phosphorylation followed by arrestin-1 binding. To test the availability of the arrestin-1 pool in dark-adapted outer segment (OS) for rhodopsin shutoff, we measured photoresponse recovery rates of mice with arrestin-1 content in the OS of 2.5%, 5%, 60%, and 100% of wild type (WT) level by two-flash ERG with the first (desensitizing) flash at 160, 400, 1000, and 2500 photons/rod. The time of half recovery (thalf) in WT retinas increases with the intensity of the initial flash, becoming ∼2.5-fold longer upon activation of 2500 than after 160 rhodopsins/rod. Mice with 60% and even 5% of WT arrestin-1 level recovered at WT rates. In contrast, the mice with 2.5% of WT arrestin-1 had a dramatically slower recovery than the other three lines, with the thalf increasing ∼28 fold between 160 and 2500 rhodopsins/rod. Even after the dimmest flash, the rate of recovery of rods with 2.5% of normal arrestin-1 was two times slower than in other lines, indicating that arrestin-1 level in the OS between 100% and 5% of WT is sufficient for rapid recovery, whereas with lower arrestin-1 the rate of recovery dramatically decreases with increased light intensity. Thus, the OS has two distinct pools of arrestin-1: cytoplasmic and a separate pool comprising ∼2.5% that is not immediately available for rhodopsin quenching. The observed delay suggests that this pool is localized at the periphery, so that its diffusion across the OS rate-limits the recovery. The line with very low arrestin-1 expression is the first where rhodopsin inactivation was made rate-limiting by arrestin manipulation. PMID:21818392

Progressive reduction of its expression in rods reveals two pools of arrestin-1 in the outer segment with different roles in photoresponse recovery.

PubMed

Cleghorn, Whitney M; Tsakem, Elviche L; Song, Xiufeng; Vishnivetskiy, Sergey A; Seo, Jungwon; Chen, Jeannie; Gurevich, Eugenia V; Gurevich, Vsevolod V

2011-01-01

Light-induced rhodopsin signaling is turned off with sub-second kinetics by rhodopsin phosphorylation followed by arrestin-1 binding. To test the availability of the arrestin-1 pool in dark-adapted outer segment (OS) for rhodopsin shutoff, we measured photoresponse recovery rates of mice with arrestin-1 content in the OS of 2.5%, 5%, 60%, and 100% of wild type (WT) level by two-flash ERG with the first (desensitizing) flash at 160, 400, 1000, and 2500 photons/rod. The time of half recovery (t(half)) in WT retinas increases with the intensity of the initial flash, becoming ∼2.5-fold longer upon activation of 2500 than after 160 rhodopsins/rod. Mice with 60% and even 5% of WT arrestin-1 level recovered at WT rates. In contrast, the mice with 2.5% of WT arrestin-1 had a dramatically slower recovery than the other three lines, with the t(half) increasing ∼28 fold between 160 and 2500 rhodopsins/rod. Even after the dimmest flash, the rate of recovery of rods with 2.5% of normal arrestin-1 was two times slower than in other lines, indicating that arrestin-1 level in the OS between 100% and 5% of WT is sufficient for rapid recovery, whereas with lower arrestin-1 the rate of recovery dramatically decreases with increased light intensity. Thus, the OS has two distinct pools of arrestin-1: cytoplasmic and a separate pool comprising ∼2.5% that is not immediately available for rhodopsin quenching. The observed delay suggests that this pool is localized at the periphery, so that its diffusion across the OS rate-limits the recovery. The line with very low arrestin-1 expression is the first where rhodopsin inactivation was made rate-limiting by arrestin manipulation.

Recapitulation of Human Retinal Development from Human Pluripotent Stem Cells Generates Transplantable Populations of Cone Photoreceptors.

PubMed

Gonzalez-Cordero, Anai; Kruczek, Kamil; Naeem, Arifa; Fernando, Milan; Kloc, Magdalena; Ribeiro, Joana; Goh, Debbie; Duran, Yanai; Blackford, Samuel J I; Abelleira-Hervas, Laura; Sampson, Robert D; Shum, Ian O; Branch, Matthew J; Gardner, Peter J; Sowden, Jane C; Bainbridge, James W B; Smith, Alexander J; West, Emma L; Pearson, Rachael A; Ali, Robin R

2017-09-12

Transplantation of rod photoreceptors, derived either from neonatal retinae or pluripotent stem cells (PSCs), can restore rod-mediated visual function in murine models of inherited blindness. However, humans depend more upon cone photoreceptors that are required for daylight, color, and high-acuity vision. Indeed, macular retinopathies involving loss of cones are leading causes of blindness. An essential step for developing stem cell-based therapies for maculopathies is the ability to generate transplantable human cones from renewable sources. Here, we report a modified 2D/3D protocol for generating hPSC-derived neural retinal vesicles with well-formed ONL-like structures containing cones and rods bearing inner segments and connecting cilia, nascent outer segments, and presynaptic structures. This differentiation system recapitulates human photoreceptor development, allowing the isolation and transplantation of a pure population of stage-matched cones. Purified human long/medium cones survive and become incorporated within the adult mouse retina, supporting the potential of photoreceptor transplantation for treating retinal degeneration. Copyright © 2017 The Authors. Published by Elsevier Inc. All rights reserved.

Constituents of Bile, Bilirubin and TUDCA, Protect Against Oxidative Stress-Induced Retinal Degeneration

PubMed Central

Oveson, Brian C.; Iwase, Takeshi; Hackett, Sean F.; Lee, Sun Young; Usui, Shinichi; Sedlak, Thomas W.; Snyder, Solomon H.; Campochiaro, Peter A.; Sung, Jennifer U.

2014-01-01

Two constituents of bile, bilirubin and tauroursodeoxycholic acid (TUDCA), have antioxidant activity. However, bilirubin can also cause damage to some neurons and glial cells, particularly immature neurons. In this study, we tested the effects of bilirubin and TUDCA in two models in which oxidative stress contributes to photoreceptor cell death, prolonged light exposure and rd10+/+ mice. In albino BALB/c mice, intraperitoneal (IP) injection of 5 mg/kg of bilirubin or 500 mg/kg of TUDCA prior to exposure to 5,000 lux of white light for 8 hours significantly reduced loss of rod and cone function assessed by electroretinograms (ERGs). Both treatments also reduced light-induced accumulation of superoxide radicals in the outer retina, rod cell death assessed by outer nuclear layer (ONL) thickness, and disruption of cone inner and outer segments. In rd10+/+ mice, IP injections of 5 or 50 mg/kg of bilirubin or 500 mg/kg of TUDCA every 3 days starting at postnatal day (P) 6, caused significant preservation of cone cell number and cone function at P50. Rods were not protected at P50, but both bilirubin and TUDCA provided modest preservation of ONL thickness and rod function at P30. These data suggest that correlation of serum bilirubin levels with rate of vision loss in patients with retinitis pigmentosa (RP) could provide a useful strategy to test the hypothesis that cones die from oxidative damage in patients with RP. If proof-of-concept is established, manipulation of bilirubin levels and administration of TUDCA could be tested in interventional trials. PMID:21054389

Bicarbonate Modulates Photoreceptor Guanylate Cyclase (ROS-GC) Catalytic Activity.

PubMed

Duda, Teresa; Wen, Xiao-Hong; Isayama, Tomoki; Sharma, Rameshwar K; Makino, Clint L

2015-04-24

By generating the second messenger cGMP in retinal rods and cones, ROS-GC plays a central role in visual transduction. Guanylate cyclase-activating proteins (GCAPs) link cGMP synthesis to the light-induced fall in [Ca(2+)]i to help set absolute sensitivity and assure prompt recovery of the response to light. The present report discloses a surprising feature of this system: ROS-GC is a sensor of bicarbonate. Recombinant ROS-GCs synthesized cGMP from GTP at faster rates in the presence of bicarbonate with an ED50 of 27 mM for ROS-GC1 and 39 mM for ROS-GC2. The effect required neither Ca(2+) nor use of the GCAPs domains; however, stimulation of ROS-GC1 was more powerful in the presence of GCAP1 or GCAP2 at low [Ca(2+)]. When applied to retinal photoreceptors, bicarbonate enhanced the circulating current, decreased sensitivity to flashes, and accelerated flash response kinetics. Bicarbonate was effective when applied either to the outer or inner segment of red-sensitive cones. In contrast, bicarbonate exerted an effect when applied to the inner segment of rods but had little efficacy when applied to the outer segment. The findings define a new regulatory mechanism of the ROS-GC system that affects visual transduction and is likely to affect the course of retinal diseases caused by cGMP toxicity. © 2015 by The American Society for Biochemistry and Molecular Biology, Inc.

Calorimetric Studies of Bovine Rod Outer Segment Disk Membranes Support a Monomeric Unit for Both Rhodopsin and Opsin

PubMed Central

Edrington, Thomas C.; Bennett, Michael; Albert, Arlene D.

2008-01-01

The photoreceptor rhodopsin is a G-protein coupled receptor that has recently been proposed to exist as a dimer or higher order oligomer, in contrast to the previously described monomer, in retinal rod outer segment disk membranes. Rhodopsin exhibits considerably greater thermal stability than opsin (the bleached form of the receptor), which is reflected in an ∼15°C difference in the thermal denaturation temperatures (Tm) of rhodopsin and opsin as measured by differential scanning calorimetry. Here we use differential scanning calorimetry to investigate the effect of partial bleaching of disk membranes on the Tm of rhodopsin and of opsin in native disk membranes, as well as in cross-linked disk membranes in which rhodopsin dimers are known to be present. The Tms of rhodopsin and opsin are expected to be perturbed if mixed oligomers are present. The Tm remained constant for rhodopsin and opsin in native disks regardless of the level of bleaching. In contrast, the Tm of cross-linked rhodopsin in disk membranes was dependent on the extent of bleaching. The energy of activation for denaturation of rhodopsin and cross-linked rhodopsin was calculated. Cross-linking rhodopsin significantly decreased the energy of activation. We conclude that in native disk membranes, rhodopsin behaves predominantly as a monomer. PMID:18586850

A variant of arrestin-1 binds rod outer segment membranes in a light-independent manner.

PubMed

Uzcanga, Graciela L; Becerra, Aniuska R; Perdomo, Deisy; Bubis, José

2011-03-15

A 50-kDa-polypeptide band peripherally bound to retinal rod outer segment (ROS) membranes was purified by anion-exchange chromatography. When the 50-kDa protein was compared with purified arrestin-1, it was observed that: (1) both proteins comigrated on sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and were recognized by either anti-50-kDa protein polyclonal antibodies or anti-arrestin-1 monoclonal antibodies; (2) protein fragments and peptide fingerprint maps obtained following limited and complete proteolysis with specific proteases were very similar for both molecules; and (3) several chromatographically-purified tryptic peptides from the 50-kDa protein possessed the same amino acid composition as tryptic peptides deduced from the reported arrestin-1 primary structure. Consequently, arrestin-1 and the purified 50-kDa protein must correspond to variants of the same molecule. However, in contrast to arrestin-1 that associated to the ROS membranes only in the presence of light and ATP, the 50-kDa protein interacted with the ROS membranes in a light-independent manner, either in the presence or absence of ATP. These results clearly established that phosphorylated and illuminated rhodopsin is not the membrane anchor for this variant of arrestin-1. Copyright © 2010 Elsevier Inc. All rights reserved.

The retinal rod Na(+)/Ca(2+),K(+) exchanger contains a noncleaved signal sequence required for translocation of the N terminus.

PubMed

McKiernan, C J; Friedlander, M

1999-12-31

The retinal rod Na(+)/Ca(2+),K(+) exchanger (RodX) is a polytopic membrane protein found in photoreceptor outer segments where it is the principal extruder of Ca(2+) ions during light adaptation. We have examined the role of the N-terminal 65 amino acids in targeting, translocation, and integration of the RodX using an in vitro translation/translocation system. cDNAs encoding human RodX and bovine RodX through the first transmembrane domain were correctly targeted and integrated into microsomal membranes; deletion of the N-terminal 65 amino acids (aa) resulted in a translation product that was not targeted or integrated. Deletion of the first 65 aa had no effect on membrane targeting of full-length RodX, but the N-terminal hydrophilic domain no longer translocated. Chimeric constructs encoding the first 65 aa of bovine RodX fused to globin were translocated across microsomal membranes, demonstrating that the sequence could function heterologously. Studies of fresh bovine retinal extracts demonstrated that the first 65 aa are present in the native protein. These data demonstrate that the first 65 aa of RodX constitute an uncleaved signal sequence required for the efficient membrane targeting and proper membrane integration of RodX.

Acute Zonal Cone Photoreceptor Outer Segment Loss.

PubMed

Aleman, Tomas S; Sandhu, Harpal S; Serrano, Leona W; Traband, Anastasia; Lau, Marisa K; Adamus, Grazyna; Avery, Robert A

2017-05-01

The diagnostic path presented narrows down the cause of acute vision loss to the cone photoreceptor outer segment and will refocus the search for the cause of similar currently idiopathic conditions. To describe the structural and functional associations found in a patient with acute zonal occult photoreceptor loss. A case report of an adolescent boy with acute visual field loss despite a normal fundus examination performed at a university teaching hospital. Results of a complete ophthalmic examination, full-field flash electroretinography (ERG) and multifocal ERG, light-adapted achromatic and 2-color dark-adapted perimetry, and microperimetry. Imaging was performed with spectral-domain optical coherence tomography (SD-OCT), near-infrared (NIR) and short-wavelength (SW) fundus autofluorescence (FAF), and NIR reflectance (REF). The patient was evaluated within a week of the onset of a scotoma in the nasal field of his left eye. Visual acuity was 20/20 OU, and color vision was normal in both eyes. Results of the fundus examination and of SW-FAF and NIR-FAF imaging were normal in both eyes, whereas NIR-REF imaging showed a region of hyporeflectance temporal to the fovea that corresponded with a dense relative scotoma noted on light-adapted static perimetry in the left eye. Loss in the photoreceptor outer segment detected by SD-OCT co-localized with an area of dense cone dysfunction detected on light-adapted perimetry and multifocal ERG but with near-normal rod-mediated vision according to results of 2-color dark-adapted perimetry. Full-field flash ERG findings were normal in both eyes. The outer nuclear layer and inner retinal thicknesses were normal. Localized, isolated cone dysfunction may represent the earliest photoreceptor abnormality or a distinct entity within the acute zonal occult outer retinopathy complex. Acute zonal occult outer retinopathy should be considered in patients with acute vision loss and abnormalities on NIR-REF imaging, especially if multimodal imaging supports an intact retinal pigment epithelium and inner retina but an abnormal photoreceptor outer segment.

Acute tissue reactions, inner segment pathology, and effects of the antioxidant α1-microglobulin in an in vitro model of retinal detachment.

PubMed

Ghosh, Fredrik; Åkerström, Bo; Bergwik, Jesper; Abdshill, Hodan; Gefors, Lina; Taylor, Linnéa

2018-04-18

The purpose of this study was to explore acute tissue reactions, ultrastructural photoreceptor morphology with emphasis on inner segments, and the effect of antioxidant treatment in an in vitro model of rhegmatogenous retinal detachment (RRD). A previously described method of RRD simulation was used with adult retinal porcine explants kept free-floating in culture medium with or without treatment with the radical scavenger α 1 -microglobulin (A1M). Explants were examined at 5 time points from 1 to 24 h using transmission electron microscopy as well as quantitative real-time PCR (RT-PCR) to quantify gene expression of the cell stress marker heat shock protein 70 (Hsp70) and oxidative stress marker heme oxygenase (HO-1). The culture medium level of the cell damage marker lactate dehydrogenase (LDH) and oxidative stress DNA damage marker 8-Oxo-2'-deoxyguanosine (8-OHdG) was also assessed at each time point. We found that the levels of Hsp70 and LDH rapidly increased in both groups, and at 3 and 6 h, Hsp70 was significantly higher in A1M treated retinas. At 24 h, Hsp70 and LDH, as well as 8-OHdG were significantly lower compared with controls, whereas the tissue level of HO-1 was significantly higher. Progressive ultrastructural photoreceptor changes were seen in untreated control explants from 1 h and onwards including outer segment shortening and loss, disruption of organelles within the inner segments and loss of perikarya in the outer nuclear layer. Inner segment pathology was more rapid and extensive in rods compared with in cones. In A1M treated counterparts, damage to rod inner segment mitochondria was significantly higher after 1 h of culture, but after this time, no statistical difference was found. At 24 h, cone inner segment mitochondrial disruption was significantly higher in control retinas and the number of surviving perikarya lower. From our results, we conclude that retinal explants elicit acute cell stress reactions when placed in culture without physical support simulating a detached retina floating in the vitreous space. Photoreceptors rapidly display degenerative changes including extensive damage to inner segment mitochondria indicating loss of energy transduction as an early key event. A1M increases initial mitochondrial stress in the rods, however, subsequent pathology is attenuated by the treatment, highlighting the dynamics of protective as well as disruptive oxidative stress reactions in the detached retina. Copyright © 2018 Elsevier Ltd. All rights reserved.

Investigation of retinal microstructure in healthy eyes and dry age-related macular degeneration using a combined AO-OCT-SLO system

NASA Astrophysics Data System (ADS)

Wells-Gray, Elaine M.; Choi, Stacey S.; Ohr, Matthew; Cebulla, Colleen M.; Doble, Nathan

2017-02-01

Combined adaptive optics (AO) optical coherence tomography (OCT) scanning laser ophthalmoscopy (SLO) imaging allows simultaneous en face and cross sectional views of the retina. We describe improvements to our AO-OCT-SLO system and highlight its resolution capability and clinical utility by presenting results from 3 control and 4 dry agerelated macular degeneration (AMD) subjects. From a group of subjects with healthy eyes, OCT A-scans were grouped as originating from cones or rods and were averaged. The resulting reflectance profiles were then used to identify the location of cone and rod segments. Results for rods and cones were compared, with the focus on inner segment (IS) and outer segment (OS) structures and where these cells embed into the retinal pigment epithelium (RPE). In the AMD patients, cone IS and OS lengths were measured over and around drusen for two retinal regions (fovea-2° and 2°-4°), and those results were correlated to drusen height. For the fovea-2° region, the drusen height that caused statistically significant shortening of cone ISL and OSL compared to the unaffected adjacent area were 40 μm and 50 μm respectively (p = 0.009, and p < 0.001, respectively). For the 2°-4° region, the equivalent drusen heights that caused significant shortening of segment length were 60 μm for IS (p = 0.017) and 80 μm for OS (p < 0.001)

Light-Emitting Diodes and Cool White Fluorescent Light Similarly Suppress Pineal Gland Melatonin and Maintain Retinal Function and Morphology in the Rat. Part 1

NASA Technical Reports Server (NTRS)

Holley, Daniel C.; Heeke, D.; Mele, G.

1999-01-01

Currently, the light sources most commonly used in animal habitat lighting are cool white fluorescent or incandescent lamps. We evaluated a novel light-emitting diode (LED) light source for use in animal habitat lighting by comparing its effectiveness to cool white fluorescent light (CWF) in suppressing pineal gland melatonin and maintaining normal retinal physiology and morphology in the rat. Results of pineal melatonin suppression experiments showed equal suppression of pineal melatonin concentrations for LED light and CWF light at five different light illuminances (100, 40, 10, 1 and 0.1 lux). There were no significant differences in melatonin suppression between LED and CWF light when compared to unexposed controls. Retinal physiology was evaluated using electroretinography. Results show no differences in a-wave implicit times and amplitudes or b-wave implicit times and amplitudes between 100-lux LED-exposed rats and 100-lux CWF-exposed rats. Results of retinal histology assessment show no differences in retinal thickness rod outer segment length and number of rod nuclei between rats exposed to 100-lux LED and 100-lux CWF for days. Furthermore, the retinal pigmented epithelium and rod outer segments of all eyes observed were in good condition and of normal thickness. This study indicates that LED light does not cause retinal damage and can suppress pineal melatonin at similar intensities as a conventional CWF light source. These data suggest that LED light sources may be suitable replacements for conventional light sources used in the lighting of rodent vivariums while providing many mechanical and economical advantages.

Immunocytochemical localization of the NMDA-R2A receptor subunit in the cat retina.

PubMed

Goebel, D J; Aurelia, J L; Tai, Q; Jojich, L; Poosch, M S

1998-10-19

Immunocytochemical studies were performed to determine the distribution and cellular localization of the NMDA-R2A receptor subunit (R2A) in the cat retina. R2A-immunoreactivity (R2A-IR) was noted in all layers of the retina, with specific localizations in the outer segments of red/green and blue cone photoreceptors, B-type horizontal cells, several types of amacrine cells, Müller cells and the majority of cells in the ganglion cell layer. In the inner nuclear layer, 48% of all cells residing in the amacrine cell layer were R2A-IR including a cell resembling the GABAergic A17 amacrine cell. Interestingly, the AII rod amacrine cell was devoid of R2A-IR. Although the localization of the R2A subunit was anticipated in ganglion cells, amacrines and Müller cells, the presence of this receptor subunit to the cells in the outer retina was not expected. Here, both the R2A and the R2B subunits were found to be present in the outer segments of cone photoreceptors and to the tips of rod outer segments. Although the function of these receptor subunits in rod and cone photoreceptors remains to be determined, the fact that both R2A and R2B receptor subunits are localized to cone outer segments suggests a possible alternative pathway for calcium entry into a region where this cation plays such a crucial role in the process of phototransduction. To further classify the cells that display NR2A-IR, we performed dual labeling experiments showing the relationship between R2A-labeled cells with GABA. Results showed that all GABAergic-amacrines and displaced amacrines express the R2A-subunit protein. In addition, approximately 11% of the NR2A-labeled amacrines, did not stain for GABA. These findings support pharmacological data showing that NMDA directly facilitates GABA release in retina and retinal cultures [I.L. Ferreira, C.B. Duarte, P.F. Santos, C.M. Carvalho, A.P. Carvalho, Release of [3H]GABA evoked by glutamate receptor agonist in cultured chick retinal cells: effect of Ca2+, Brain Res. 664 (1994) 252-256; G.D. Zeevalk, W.J. Nicklas, Action of the anti-ischemic agent ifenprodil on N-methyl-d-aspartate and kainate-mediated excitotoxicity, Brain Res. 522 (1990) 135-139; R. Huba, H.D. Hofmann, Transmitter-gated currents of GABAergic amacrine-like cells in chick retinal cultures, Vis. Neurosci. 6 (1991) 303-314; M. Yamashita, R. Huba, H.D. Hofmann, Early in vitro development of voltage- and transmitter-gated currents in GABAergic amacrine cells, Dev. Brain Res. 82 (1994) 95-102; R. Ientile, S. Pedale, V. Picciurro, V. Macaione, C. Fabiano, S. Macaione, Nitric oxide mediates NMDA-evoked [3H]GABA release from chick retina cells, FEBS Lett. 417 (1997) 345-348; R.C. Kubrusly, M.C. deMello, F.G. deMello, Aspartate as a selective NMDA agonist in cultured cells from the avian retina, Neurochem. Intl. 32 (1998) 47-52] or reduction of GABA in vivo [N.N. Osborn, A.J. Herrera, The effect of experimental ischaemia and excitatory amino acid agonist on the GABA and serotonin immunoreactivities in the rabbit retina, Neurosci. 59 (1994) 1071-1081]. Since the majority of GABAergic synapses in the inner retina are onto both rod and cone bipolar axon terminals [R.G. Pourcho, M.T. Owzcarzak, Distribution of GABA immunoreactivity in the cat retina: A light and electron-microscopic study, Vis. Neurosci. 2 (1989) 425-435], we hypothesize that the NMDA-receptor plays a crucial role in providing feedback inhibition onto rod and cone bipolar cells. Copyright 1998 Elsevier Science B.V.

Histologic development of the human fovea from midgestation to maturity.

PubMed

Hendrickson, Anita; Possin, Daniel; Vajzovic, Lejla; Toth, Cynthia A

2012-11-01

To describe the histologic development of the human central retina from fetal week (Fwk) 22 to 13 years. Retrospective observational case series. Retinal layers and neuronal substructures were delineated on foveal sections of fixed tissue stained in azure II-methylene blue and on frozen sections immunolabeled for cone, rod, or glial proteins. Postmortem tissue was from 11 eyes at Fwk 20-27; 8 eyes at Fwk 28-37; 6 eyes at postnatal 1 day to 6 weeks; 3 eyes at 9 to 15 months; and 5 eyes at 28 months to 13 years. At Fwk 20-22 the fovea could be identified by the presence of a single layer of cones in the outer nuclear layer. Immunolabeling detected synaptic proteins, cone and rod opsins, and Müller glial processes separating the photoreceptors. The foveal pit appeared at Fwk 25, involving progressive peripheral displacement of ganglion cell, inner plexiform, and inner nuclear layers. The pit became wider and shallower after birth, and appeared mature by 15 months. Between Fwk 25 and Fwk 38, all photoreceptors developed more distinct inner and outer segments, but these were longer on peripheral than foveal cones. After birth the foveal outer nuclear layer became much thicker as cone packing occurred. Cone packing and neuronal migration during pit formation combined to form long central photoreceptor axons, which changed the outer plexiform layer from a thin sheet of synaptic pedicles into the thickest layer in the central retina by 15 months. Foveal inner and outer segment length matched peripheral cones by 15 months and was 4 times longer by 13 years. These data are necessary to understand the marked changes in human retina from late gestation to early adulthood. They provide qualitative and quantitative morphologic information required to interpret the changes in hyper- and hyporeflexive bands in pediatric spectral-domain optical coherence tomography images at the same ages. Copyright © 2012 Elsevier Inc. All rights reserved.

The kinetics of inactivation of the rod phototransduction cascade with constant Ca2+i

PubMed Central

1996-01-01

A rich variety of mechanisms govern the inactivation of the rod phototransduction cascade. These include rhodopsin phosphorylation and subsequent binding of arrestin; modulation of rhodopsin kinase by S- modulin (recoverin); regulation of G-protein and phosphodiesterase inactivation by GTPase-activating factors; and modulation of guanylyl cyclase by a high-affinity Ca(2+)-binding protein. The dependence of several of the inactivation mechanisms on Ca2+i makes it difficult to assess the contributions of these mechanisms to the recovery kinetics in situ, where Ca2+i is dynamically modulated during the photoresponse. We recorded the circulating currents of salamander rods, the inner segments of which are held in suction electrodes in Ringer's solution. We characterized the response kinetics to flashes under two conditions: when the outer segments are in Ringer's solution, and when they are in low-Ca2+ choline solutions, which we show clamp Ca2+i very near its resting level. At T = 20-22 degrees C, the recovery phases of responses to saturating flashes producing 10(2.5)-10(4.5) photoisomerizations under both conditions are characterized by a dominant time constant, tau c = 2.4 +/- 0.4 s, the value of which is not dependent on the solution bathing the outer segment and therefore not dependent on Ca2+i. We extended a successful model of activation by incorporating into it a first-order inactivation of R*, and a first-order, simultaneous inactivation of G-protein (G*) and phosphodiesterase (PDE*). We demonstrated that the inactivation kinetics of families of responses obtained with Ca2+i clamped to rest are well characterized by this model, having one of the two inactivation time constants (tau r* or tau PDE*) equal to tau c, and the other time constant equal to 0.4 +/- 0.06 s. PMID:8741728

Live Imaging of LysoTracker-Labelled Phagolysosomes Tracks Diurnal Phagocytosis of Photoreceptor Outer Segment Fragments in Rat RPE Tissue Ex Vivo.

PubMed

Mao, Yingyu; Finnemann, Silvia C

2016-01-01

Renewal of rod photoreceptor outer segments in the mammalian eye involves synchronized diurnal shedding after light onset of spent distal outer segment fragments (POS) linked to swift clearance of shed POS from the subretinal space by the adjacent retinal pigment epithelium (RPE). Engulfed POS phagosomes in RPE cells mature to acidified phagolysosomes, which accomplish enzymatic degradation of POS macromolecules. Here, we used an acidophilic fluorophore LysoTracker to label acidic organelles in freshly dissected, live rat RPE tissue flat mounts. We observed that all RPE cells imaged contained numerous acidified POS phagolysosomes whose abundance per cell was dramatically increased 2 h after light onset as compared to either 1 h before or 4 h after light onset. Lack of organelles of similar diameter (of 1-2 μm) in phagocytosis-defective mutant RCS rat RPE confirmed that LysoTracker live imaging detected POS phagolysosomes. Lack of increase in lysosomal membrane protein LAMP-1 in RPE/choroid during the diurnal phagocytic burst suggests that formation of POS phagolysosomes in RPE in situ may not involve extra lysosome membrane biogenesis. Taken together, we report a new imaging approach that directly detects POS phagosome acidification and allows rapid tracking and quantification of POS phagocytosis by live RPE -tissue ex situ.

The physiological roles of arrestin-1 in rod photoreceptor cells.

PubMed

Chen, Jeannie

2014-01-01

Arrestin-1 is the second most abundant protein in rod photoreceptors and is nearly equimolar to rhodopsin. Its well-recognized role is to "arrest" signaling from light-activated, phosphorylated rhodopsin, a prototypical G protein-coupled receptor. In doing so, arrestin-1 plays a key role in the rapid recovery of the light response. Arrestin-1 exists in a basal conformation that is stabilized by two independent sets of intramolecular interactions. The intramolecular constraints are disrupted by encountering (1) active conformation of the receptor (R*) and (2) receptor-attached phosphates. Requirement for these two events ensures its highly specific high-affinity binding to phosphorylated, light-activated rhodopsin (P-R*). In the dark-adapted state, the basal form is further organized into dimers and tetramers. Emerging data suggest pleiotropic roles of arrestin-1 beyond the functional range of rod cells. These include light-induced arrestin-1 translocation from the inner segment to the outer segment, a process that may be protective against cellular damage incurred by constitutive signaling. Its expanding list of binding partners also hints at additional, yet to be characterized functions. Uncovering these novel roles of arrestin-1 is a subject of future studies.

The Effects of Diabetic Retinopathy and Pan-Retinal Photocoagulation on Photoreceptor Cell Function as Assessed by Dark Adaptometry

PubMed Central

Bavinger, J. Clay; Dunbar, Grace E.; Stem, Maxwell S.; Blachley, Taylor S.; Kwark, Leon; Farsiu, Sina; Jackson, Gregory R.; Gardner, Thomas W.

2016-01-01

Purpose The pathophysiology of vision loss in persons with diabetic retinopathy (DR) is complex and incompletely defined. We hypothesized that retinal pigment epithelium (RPE) and rod and cone photoreceptor dysfunction, as measured by dark adaptometry, would increase with severity of DR, and that pan-retinal photocoagulation (PRP) would exacerbate this dysfunction. Methods Dark adaptation (DA) was measured in subjects with diabetes mellitus and healthy controls. Dark adaptation was measured at 5° superior to the fovea following a flash bleach, and the data were analyzed to yield cone and rod sensitivity curves. Retinal layer thicknesses were quantified using spectral-domain optical coherence tomography (OCT). Results The sample consisted of 23 controls and 73 diabetic subjects. Subjects with moderate nonproliferative diabetic retinopathy (NPDR) exhibited significant impairment of rod recovery rate compared with control subjects (P = 0.04). Cone sensitivity was impaired in subjects with proliferative diabetic retinopathy (PDR) (type 1 diabetes mellitus [T1DM]: P = 0.0047; type 2 diabetes mellitus [T2DM]: P < 0.001). Subjects with untreated PDR compared with subjects treated with PRP exhibited similar rod recovery rates and cone sensitivities. Thinner RPE as assessed by OCT was associated with slower rod recovery and lower cone sensitivity, and thinner photoreceptor inner segment/outer segment layer was associated with lower cone sensitivity. Conclusions The results suggest that RPE and photoreceptor cell dysfunction, as assessed by cone sensitivity level and rod- and RPE-mediated dark adaptation, progresses with worsening DR, and rod recovery dysfunction occurs earlier than cone dysfunction. Function was preserved following PRP. The findings suggest multiple defects in retinoid function and provide potential points to improve visual function in persons with PDR. PMID:26803796

Early photoreceptor outer segment loss and retinoschisis in Cohen syndrome.

PubMed

Uyhazi, Katherine E; Binenbaum, Gil; Carducci, Nicholas; Zackai, Elaine H; Aleman, Tomas S

2018-06-01

To describe early structural and functional retinal changes in a patient with Cohen syndrome. A 13-month-old Caucasian girl of Irish and Spanish ancestry was noted to have micrognathia and laryngomalacia at birth, which prompted a genetic evaluation that revealed biallelic deletions in COH1 (VPS13B) (a maternally inherited 60-kb deletion involving exons 26-32 and a paternally inherited 3.5-kb deletion within exon 17) consistent with Cohen syndrome. She underwent a complete ophthalmic examination, full-field flash electroretinography and retinal imaging with spectral domain optical coherence tomography. Central vision was central, steady, and maintained. There was bilateral myopic astigmatic refractive error. Fundus exam was notable for dark foveolar pigmentation, but no obvious abnormalities of either eye. Spectral domain optical coherence tomography cross sections through the fovea revealed a normal appearing photoreceptor outer nuclear layer but loss of the interdigitation signal between the photoreceptor outer segments and the apical retinal pigment epithelium. Retinoschisis involving the inner nuclear layer of both eyes and possible ganglion cell layer thinning were also noted. There was a detectable electroretinogram with similarly reduced amplitudes of rod- (white, 0.01 cd.s.m -2 ) and cone-mediated (3 cd.s.m -2 , 30 Hz) responses. Photoreceptor outer segment abnormalities and retinoschisis may represent the earliest structural retinal change detected by spectral domain optical coherence tomography in patients with Cohen syndrome, suggesting a complex pathophysiology with primary involvement of the photoreceptor cilium and disorganization of the structural integrity of the inner retina.

The rod-driven a-wave of the dark-adapted mammalian electroretinogram.

PubMed

Robson, John G; Frishman, Laura J

2014-03-01

The a-wave of the electroretinogram (ERG) reflects the response of photoreceptors to light, but what determines the exact waveform of the recorded voltage is not entirely understood. We have now simulated the trans-retinal voltage generated by the photocurrent of dark-adapted mammalian rods, using an electrical model based on the in vitro measurements of Hagins et al. (1970) and Arden (1976) in rat retinas. Our simulations indicate that in addition to the voltage produced by extracellular flow of photocurrent from rod outer to inner segments, a substantial fraction of the recorded a-wave is generated by current that flows in the outer nuclear layer (ONL) to hyperpolarize the rod axon and synaptic terminal. This current includes a transient capacitive component that contributes an initial negative "nose" to the trans-retinal voltage when the stimulus is strong. Recordings in various species of the a-wave, including the peak and initial recovery towards the baseline, are consistent with simulations showing an initial transient primarily related to capacitive currents in the ONL. Existence of these capacitive currents can explain why there is always a substantial residual transient a-wave when post-receptoral responses are pharmacologically inactivated in rodents and nonhuman primates, or severely genetically compromised in humans (e.g. complete congenital stationary night blindness) and nob mice. Our simulations and analysis of ERGs indicate that the timing of the leading edge and peak of dark-adapted a-waves evoked by strong stimuli could be used in a simple way to estimate rod sensitivity. Copyright © 2013 Elsevier Ltd. All rights reserved.

Acute Zonal Cone Photoreceptor Outer Segment Loss

PubMed Central

Sandhu, Harpal S.; Serrano, Leona W.; Traband, Anastasia; Lau, Marisa K.; Adamus, Grazyna; Avery, Robert A.

2017-01-01

Importance The diagnostic path presented narrows down the cause of acute vision loss to the cone photoreceptor outer segment and will refocus the search for the cause of similar currently idiopathic conditions. Objective To describe the structural and functional associations found in a patient with acute zonal occult photoreceptor loss. Design, Setting, and Participants A case report of an adolescent boy with acute visual field loss despite a normal fundus examination performed at a university teaching hospital. Main Outcomes and Measures Results of a complete ophthalmic examination, full-field flash electroretinography (ERG) and multifocal ERG, light-adapted achromatic and 2-color dark-adapted perimetry, and microperimetry. Imaging was performed with spectral-domain optical coherence tomography (SD-OCT), near-infrared (NIR) and short-wavelength (SW) fundus autofluorescence (FAF), and NIR reflectance (REF). Results The patient was evaluated within a week of the onset of a scotoma in the nasal field of his left eye. Visual acuity was 20/20 OU, and color vision was normal in both eyes. Results of the fundus examination and of SW-FAF and NIR-FAF imaging were normal in both eyes, whereas NIR-REF imaging showed a region of hyporeflectance temporal to the fovea that corresponded with a dense relative scotoma noted on light-adapted static perimetry in the left eye. Loss in the photoreceptor outer segment detected by SD-OCT co-localized with an area of dense cone dysfunction detected on light-adapted perimetry and multifocal ERG but with near-normal rod-mediated vision according to results of 2-color dark-adapted perimetry. Full-field flash ERG findings were normal in both eyes. The outer nuclear layer and inner retinal thicknesses were normal. Conclusions and Relevance Localized, isolated cone dysfunction may represent the earliest photoreceptor abnormality or a distinct entity within the acute zonal occult outer retinopathy complex. Acute zonal occult outer retinopathy should be considered in patients with acute vision loss and abnormalities on NIR-REF imaging, especially if multimodal imaging supports an intact retinal pigment epithelium and inner retina but an abnormal photoreceptor outer segment. PMID:28384671

Photoreceptor Layer Thickness Changes During Dark Adaptation Observed With Ultrahigh-Resolution Optical Coherence Tomography.

PubMed

Lu, Chen D; Lee, ByungKun; Schottenhamml, Julia; Maier, Andreas; Pugh, Edward N; Fujimoto, James G

2017-09-01

To examine outer retinal band changes after flash stimulus and subsequent dark adaptation with ultrahigh-resolution optical coherence tomography (UHR-OCT). Five dark-adapted left eyes of five normal subjects were imaged with 3-μm axial-resolution UHR-OCT during 30 minutes of dark adaptation following 96%, 54%, 23%, and 0% full-field and 54% half-field rhodopsin bleach. We identified the ellipsoid zone inner segment/outer segment (EZ[IS/OS]), cone interdigitation zone (CIZ), rod interdigitation zone (RIZ), retinal pigment epithelium (RPE), and Bruch's membrane (BM) axial positions and generated two-dimensional thickness maps of the EZ(IS/OS) to the four bands. The average thickness over an area of the thickness map was compared against that of the dark-adapted baselines. The time-dependent thickness changes (photoresponses) were statistically compared against 0% bleach. Dark adaptometry was performed with the same bleaching protocol. The EZ(IS/OS)-CIZ photoresponse was significantly different at 96% (P < 0.0001) and 54% (P = 0.006) bleach. At all three bleaching levels, the EZ(IS/OS)-RIZ, -RPE, and -BM responses were significantly different (P < 0.0001). The EZ(IS/OS)-CIZ and EZ(IS/OS)-RIZ time courses were similar to the recovery of rod- and cone-mediated sensitivity, respectively, measured with dark adaptometry. The maximal EZ(IS/OS)-CIZ and EZ(IS/OS)-RIZ response magnitudes doubled from 54% to 96% bleach. Both EZ(IS/OS)-RPE and EZ(IS/OS)-BM responses resembled dampened oscillations that were graded in amplitude and duration with bleaching intensity. Half-field photoresponses were localized to the stimulated retina. With noninvasive, near-infrared UHR-OCT, we characterized three distinct, spatially localized photoresponses in the outer retinal bands. These photoresponses have potential value as physical correlates of photoreceptor function.

Outer Retinal Changes Including the Ellipsoid Zone Band in Usher Syndrome 1B due to MYO7A Mutations.

PubMed

Sumaroka, Alexander; Matsui, Rodrigo; Cideciyan, Artur V; McGuigan, David B; Sheplock, Rebecca; Schwartz, Sharon B; Jacobson, Samuel G

2016-07-01

To study transition zones from normal to abnormal retina in Usher syndrome IB (USH1B) caused by myosin 7A (MYO7A) mutations. Optical coherence tomography (OCT) scattering layers in outer retina were segmented in patients (n = 16, ages 2-42; eight patients had serial data, average interval 4.5 years) to quantify outer nuclear layer (ONL) and outer segments (OS) as well as the locus of EZ (ellipsoid zone) edge and its extent from the fovea. Static perimetry was measured under dark-adapted (DA) and light-adapted (LA) conditions. Ellipsoid zone edge in USH1B-MYO7A could be located up to 23° from the fovea. Ellipsoid zone extent constricted at a rate of 0.51°/year with slower rates at smaller eccentricities. A well-defined EZ line could be associated with normal or abnormal ONL and/or OS thickness; detectable ONL extended well beyond EZ edge. At the EZ edge, the local slope of LA sensitivity loss was 2.6 (±1.7) dB/deg for central transition zones. At greater eccentricities, the local slope of cone sensitivity loss was shallower (1.1 ± 0.4 dB/deg for LA) than that of rod sensitivity loss (2.8 ± 1.2 dB/deg for DA). In USH1B-MYO7A, constriction rate of EZ extent depends on the initial eccentricity of the transition. Ellipsoid zone edges in the macula correspond to large local changes in cone vision, but extramacular EZ edges show more pronounced losses on rod-based vision tests. It is advisable to use not only the EZ line but also other structural and functional parameters for estimating natural history of disease and possible therapeutic effects in future clinical trials of USH1B-MYO7A.

Control rod driveline and grapple

DOEpatents

Germer, John H.

1987-01-01

A control rod driveline and grapple is disclosed for placement between a control rod drive and a nuclear reactor control rod containing poison for parasitic neutron absorption required for reactor shutdown. The control rod is provided with an enlarged cylindrical handle which terminates in an upwardly extending rod to provide a grapple point for the driveline. The grapple mechanism includes a tension rod which receives the upwardly extending handle and is provided with a lower annular flange. A plurality of preferably six grapple segments surround and grip the control rod handle. Each grapple rod segment grips the flange on the tension rod at an interior upper annular indentation, bears against the enlarged cylindrical handle at an intermediate annulus and captures the upwardly flaring frustum shaped handle at a lower and complementary female segment. The tension rods and grapple segments are surrounded by and encased within a cylinder. The cylinder terminates immediately and outward extending annulus at the lower portion of the grapple segments. Excursion of the tension rod relative to the encasing cylinder causes rod release at the handle by permitting the grapple segments to pivot outwardly and about the annulus on the tension rod so as to open the lower defined frustum shaped annulus and drop the rod. Relative movement between the tension rod and cylinder can occur either due to electromagnetic release of the tension rod within defined limits of travel or differential thermal expansion as between the tension rod and cylinder as where the reactor exceeds design thermal limits.

Mutation K42E in dehydrodolichol diphosphate synthase (DHDDS) causes recessive retinitis pigmentosa.

PubMed

Lam, Byron L; Züchner, Stephan L; Dallman, Julia; Wen, Rong; Alfonso, Eduardo C; Vance, Jeffery M; Peričak-Vance, Margaret A

2014-01-01

A single-nucleotide mutation in the gene that encodes DHDDS has been identified by whole exome sequencing as the cause of the non-syndromic recessive retinitis pigmentosa (RP) in a family of Ashkenazi Jewish origin in which three of the four siblings have early onset retinal degeneration. The peripheral retinal degeneration in the affected siblings was evident in the initial examination in 1992 and only one had detectable electroretinogram (ERG) that suggested cone-rod dysfunction. The pigmentary retinal degeneration subsequently progressed rapidly. The identified mutation changes the highly conserved residue Lys42 to Glu, resulting in lower catalytic efficiency. Patterns of plasma transferrin isoelectric focusing gel were normal in all family members, indicating no significant abnormality in protein glycosylation. Dolichols have been shown to influence the fluidity and of the membrane and promote vesicle fusion. Considering that photoreceptor outer segments contain stacks of membrane discs, we believe that the mutation may lead to low dolichol levels in photoreceptor outer segments, resulting in unstable membrane structure that leads to photoreceptor degeneration.

Light responses in rods of vitamin A-deprived Xenopus.

PubMed

Solessio, Eduardo; Umino, Yumiko; Cameron, David A; Loew, Ellis; Engbretson, Gustav A; Knox, Barry E; Barlow, Robert B

2009-09-01

Accumulation of free opsin by mutations in rhodopsin or insufficiencies in the visual cycle can lead to retinal degeneration. Free opsin activates phototransduction; however, the link between constitutive activation and retinal degeneration is unclear. In this study, the photoresponses of Xenopus rods rendered constitutively active by vitamin A deprivation were examined. Unlike their mammalian counterparts, Xenopus rods do not degenerate. Contrasting phototransduction in vitamin A-deprived Xenopus rods with phototransduction in constitutively active mammalian rods may provide new understanding of the mechanisms that lead to retinal degeneration. The photocurrents of Xenopus tadpole rods were measured with suction electrode recordings, and guanylate cyclase activity was measured with the IBMX (3-isobutyl-1-methylxanthine) jump technique. The amount of rhodopsin in rods was determined by microspectrophotometry. The vitamin A-deprived rod outer segments were 60% to 70% the length and diameter of the rods in age-matched animals. Approximately 90% of its opsin content was in the free or unbound form. Analogous to bleaching adaptation, the photoresponses were desensitized (10- to 20-fold) and faster. Unlike bleaching adaptation, the vitamin A-deprived rods maintained near normal saturating (dark) current densities by developing abnormally high rates of cGMP synthesis. Their rate of cGMP synthesis in the dark (15 seconds(-1)) was twofold greater than the maximum levels attainable by control rods ( approximately 7 seconds(-1)). Preserving circulating current density and response range appears to be an important goal for rod homeostasis. However, the compensatory changes associated with vitamin A deprivation in Xenopus rods come at the high metabolic cost of a 15-fold increase in basal ATP consumption.

Morphological evidence of neurotoxicity in retina after methylmercury exposure.

PubMed

Mela, Maritana; Grötzner, Sonia Regina; Legeay, Alexia; Mesmer-Dudons, Nathalie; Massabuau, Jean-Charles; Ventura, Dora Fix; de Oliveira Ribeiro, Ciro Alberto

2012-06-01

The visual system is particularly sensitive to methylmercury (MeHg) exposure and, therefore, provides a useful model for investigating the fundamental mechanisms that direct toxic effects. During a period of 70 days, adult of a freshwater fish species Hoplias malabaricus were fed with fish prey previously labeled with two different doses of methylmercury (0.075 and 0.75 μgg(-1)) to determine the mercury distribution and morphological changes in the retina. Mercury deposits were found in the photoreceptor layer, in the inner plexiform layer and in the outer plexiform layer, demonstrating a dose-dependent bioaccumulation. The ultrastructure analysis of retina revealed a cellular deterioration in the photoreceptor layer, morphological changes in the inner and outer segments of rods, structural changes in the plasma membrane of rods and double cones, changes in the process of removal of membranous discs and a structural discontinuity. These results lead to the conclusion that methylmercury is able to cross the blood-retina barrier, accumulate in the cells and layers of retina and induce changes in photoreceptors of H. malabaricus even under subchronic exposure. Copyright © 2012 Elsevier Inc. All rights reserved.

Biophysical mechanism of transient retinal phototropism in rod photoreceptors.

PubMed

Zhao, Xiaohui; Thapa, Damber; Wang, Benquan; Gai, Shaoyan; Yao, Xincheng

2016-02-13

Oblique light stimulation evoked transient retinal phototropism (TRP) has been recently detected in frog and mouse retinas. High resolution microscopy of freshly isolated retinas indicated that the TRP is predominated by rod photoreceptors. Comparative confocal microscopy and optical coherence tomography (OCT) revealed that the TRP predominantly occurred from the photoreceptor outer segment (OS). However, biophysical mechanism of rod OS change is still unknown. In this study, frog retinal slices, which open a cross section of retinal photoreceptor and other functional layers, were used to test the effect of light stimulation on rod OS. Near infrared light microscopy was employed to monitor photoreceptor changes in retinal slices stimulated by a rectangular-shaped visible light flash. Rapid rod OS length change was observed after the stimulation delivery. The magnitude and direction of the rod OS change varied with the position of the rods within the stimulated area. In the center of stimulated region the length of the rod OS shrunk, while in the peripheral region the rod OS tip swung towards center region in the plane perpendicular to the incident stimulus light. Our experimental result and theoretical analysis suggest that the observed TRP may reflect unbalanced disc-shape change due to localized pigment bleaching. Further investigation is required to understand biochemical mechanism of the observed rod OS kinetics. Better study of the TRP may provide a noninvasive biomarker to enable early detection of age-related macular degeneration (AMD) and other diseases that are known to produce retinal photoreceptor dysfunctions.

Biophysical mechanism of transient retinal phototropism in rod photoreceptors

NASA Astrophysics Data System (ADS)

Zhao, Xiaohui; Thapa, Damber; Wang, Benquan; Gai, Shaoyan; Yao, Xincheng

2016-03-01

Oblique light stimulation evoked transient retinal phototropism (TRP) has been recently detected in frog and mouse retinas. High resolution microscopy of freshly isolated retinas indicated that the TRP is predominated by rod photoreceptors. Comparative confocal microscopy and optical coherence tomography (OCT) revealed that the TRP predominantly occurred from the photoreceptor outer segment (OS). However, biophysical mechanism of rod OS change is still unknown. In this study, frog retinal slices, which open a cross section of retinal photoreceptor and other functional layers, were used to test the effect of light stimulation on rod OS. Near infrared light microscopy was employed to monitor photoreceptor changes in retinal slices stimulated by a rectangular-shaped visible light flash. Rapid rod OS length change was observed after the stimulation delivery. The magnitude and direction of the rod OS change varied with the position of the rods within the stimulated area. In the center of stimulated region the length of the rod OS shrunk, while in the peripheral region the rod OS tip swung towards center region in the plane perpendicular to the incident stimulus light. Our experimental result and theoretical analysis suggest that the observed TRP may reflect unbalanced disc-shape change due to localized pigment bleaching. Further investigation is required to understand biochemical mechanism of the observed rod OS kinetics. Better study of the TRP may provide a noninvasive biomarker to enable early detection of age-related macular degeneration (AMD) and other diseases that are known to produce retinal photoreceptor dysfunctions.

Rod-Coil Block Polyimide Copolymers

NASA Technical Reports Server (NTRS)

Meador, Mary Ann B. (Inventor); Kinder, James D. (Inventor)

2005-01-01

This invention is a series of rod-coil block polyimide copolymers that are easy to fabricate into mechanically resilient films with acceptable ionic or protonic conductivity at a variety of temperatures. The copolymers consist of short-rigid polyimide rod segments alternating with polyether coil segments. The rods and coil segments can be linear, branched or mixtures of linear and branched segments. The highly incompatible rods and coil segments phase separate, providing nanoscale channels for ion conduction. The polyimide segments provide dimensional and mechanical stability and can be functionalized in a number of ways to provide specialized functions for a given application. These rod-coil black polyimide copolymers are particularly useful in the preparation of ion conductive membranes for use in the manufacture of fuel cells and lithium based polymer batteries.

Platelet-Derived Growth Factor-BB Lessens Light-Induced Rod Photoreceptor Damage in Mice.

PubMed

Takahashi, Kei; Shimazawa, Masamitsu; Izawa, Hiroshi; Inoue, Yuki; Kuse, Yoshiki; Hara, Hideaki

2017-12-01

Platelet-derived growth factor (PDGF)-BB is known to have neuroprotective effects against various neurodegenerative disorders. The purpose of this study was to determine whether PDGF-BB can be neuroprotective against light-induced photoreceptor damage in mice. Mice were exposed to 8000-lux luminance for 3 hours to induce phototoxicity. Two hours before light exposure, the experimental mice were injected with PDGF-BB intravitreally, and the control mice were injected with phosphate-buffered saline. The light-exposed PDGF-BB-injected mice and saline-injected mice were evaluated electroretinographically and histologically. The site and expression levels of PDGFR-β and PDGF-BB were determined by immunostaining and Western blotting, respectively. The effect of PDGF-BB on light-induced cone and rod photoreceptor damage was also evaluated in vitro in 661W cells, a murine cone photoreceptor cell line, and in primary retinal cell cultures. An intravitreal injection of PDGF-BB significantly reduced the decrease in the amplitudes of the electroretinograms (ERGs) and the thinning of the outer nuclear layer (ONL) induced by the light exposure. It also reduced the number of TUNEL-positive cells in the ONL. PDGFR-β was expressed in the rod outer segments (OSs) but not the cone OSs. The levels of PDGF-BB and PDGFR-β were decreased after light irradiation. In addition, PDGF-BB had protective effects against light-induced damage to cells of rod photoreceptors but had no effect on the 661W cells in vitro. These findings indicate that PDGF-BB reduces the degree of light-induced retinal damage by activating PDGFR-β in rod photoreceptors. These findings suggest that PDGF-BB could play a role in the prevention of degeneration in eyes susceptible to phototoxicity.

In Vivo Imaging of Human Cone Photoreceptor Inner Segments

PubMed Central

Scoles, Drew; Sulai, Yusufu N.; Langlo, Christopher S.; Fishman, Gerald A.; Curcio, Christine A.; Carroll, Joseph; Dubra, Alfredo

2014-01-01

Purpose. An often overlooked prerequisite to cone photoreceptor gene therapy development is residual photoreceptor structure that can be rescued. While advances in adaptive optics (AO) retinal imaging have recently enabled direct visualization of individual cone and rod photoreceptors in the living human retina, these techniques largely detect strongly directionally-backscattered (waveguided) light from normal intact photoreceptors. This represents a major limitation in using existing AO imaging to quantify structure of remnant cones in degenerating retina. Methods. Photoreceptor inner segment structure was assessed with a novel AO scanning light ophthalmoscopy (AOSLO) differential phase technique, that we termed nonconfocal split-detector, in two healthy subjects and four subjects with achromatopsia. Ex vivo preparations of five healthy donor eyes were analyzed for comparison of inner segment diameter to that measured in vivo with split-detector AOSLO. Results. Nonconfocal split-detector AOSLO reveals the photoreceptor inner segment with or without the presence of a waveguiding outer segment. The diameter of inner segments measured in vivo is in good agreement with histology. A substantial number of foveal and parafoveal cone photoreceptors with apparently intact inner segments were identified in patients with the inherited disease achromatopsia. Conclusions. The application of nonconfocal split-detector to emerging human gene therapy trials will improve the potential of therapeutic success, by identifying patients with sufficient retained photoreceptor structure to benefit the most from intervention. Additionally, split-detector imaging may be useful for studies of other retinal degenerations such as AMD, retinitis pigmentosa, and choroideremia where the outer segment is lost before the remainder of the photoreceptor cell. PMID:24906859

The evolution of rod photoreceptors

PubMed Central

Morshedian, Ala

2017-01-01

Photoreceptors in animals are generally of two kinds: the ciliary or c-type and the rhabdomeric or r-type. Although ciliary photoreceptors are found in many phyla, vertebrates seem to be unique in having two distinct kinds which together span the entire range of vision, from single photons to bright light. We ask why the principal photoreceptors of vertebrates are ciliary and not rhabdomeric, and how rods evolved from less sensitive cone-like photoreceptors to produce our duplex retina. We suggest that the principal advantage of vertebrate ciliary receptors is that they use less ATP than rhabdomeric photoreceptors. This difference may have provided sufficient selection pressure for the development of a completely ciliary eye. Although many of the details of rod evolution are still uncertain, present evidence indicates that (i) rods evolved very early before the split between the jawed and jawless vertebrates, (ii) outer-segment discs make no contribution to rod sensitivity but may have evolved to increase the efficiency of protein renewal, and (iii) evolution of the rod was incremental and multifaceted, produced by the formation of several novel protein isoforms and by changes in protein expression, with no one alteration having more than a few-fold effect on transduction activation or inactivation. This article is part of the themed issue ‘Vision in dim light’. PMID:28193819

The evolution of rod photoreceptors.

PubMed

Morshedian, Ala; Fain, Gordon L

2017-04-05

Photoreceptors in animals are generally of two kinds: the ciliary or c-type and the rhabdomeric or r-type. Although ciliary photoreceptors are found in many phyla, vertebrates seem to be unique in having two distinct kinds which together span the entire range of vision, from single photons to bright light. We ask why the principal photoreceptors of vertebrates are ciliary and not rhabdomeric, and how rods evolved from less sensitive cone-like photoreceptors to produce our duplex retina. We suggest that the principal advantage of vertebrate ciliary receptors is that they use less ATP than rhabdomeric photoreceptors. This difference may have provided sufficient selection pressure for the development of a completely ciliary eye. Although many of the details of rod evolution are still uncertain, present evidence indicates that (i) rods evolved very early before the split between the jawed and jawless vertebrates, (ii) outer-segment discs make no contribution to rod sensitivity but may have evolved to increase the efficiency of protein renewal, and (iii) evolution of the rod was incremental and multifaceted, produced by the formation of several novel protein isoforms and by changes in protein expression, with no one alteration having more than a few-fold effect on transduction activation or inactivation.This article is part of the themed issue 'Vision in dim light'. © 2017 The Author(s).

The retinal phenotype of Usher syndrome: pathophysiological insights from animal models.

PubMed

El-Amraoui, Aziz; Petit, Christine

2014-03-01

The Usher syndrome (USH) is the most prevalent cause of inherited deaf-blindness. Three clinical subtypes, USH1-3, have been defined, and ten USH genes identified. The hearing impairment due to USH gene defects has been shown to result from improper organisation of the hair bundle, the sound receptive structure of sensory hair cells. In contrast, the cellular basis of the visual defect is less well understood as this phenotype is absent in almost all the USH mouse models that faithfully mimic the human hearing impairment. Structural and molecular interspecies discrepancies regarding photoreceptor calyceal processes and the association with the distribution of USH1 proteins have recently been unravelled, and have led to the conclusion that a defect in the USH1 protein complex-mediated connection between the photoreceptor outer segment and the surrounding calyceal processes (in both rods and cones), and the inner segment (in rods only), probably causes the USH1 retinal dystrophy in humans. Copyright © 2013 Académie des sciences. Published by Elsevier SAS. All rights reserved.

Gene replacement therapy for retinal CNG channelopathies.

PubMed

Schön, Christian; Biel, Martin; Michalakis, Stylianos

2013-10-01

Visual phototransduction relies on the function of cyclic nucleotide-gated channels in the rod and cone photoreceptor outer segment plasma membranes. The role of these ion channels is to translate light-triggered changes in the second messenger cyclic guanosine 3'-5'-monophosphate levels into an electrical signal that is further processed within the retinal network and then sent to higher visual centers. Rod and cone photoreceptors express distinct CNG channels. The rod photoreceptor CNG channel is composed of one CNGB1 and three CNGA1 subunits, whereas the cone channel is formed by one CNGB3 and three CNGA3 subunits. Mutations in any of these channel subunits result in severe and currently untreatable retinal degenerative diseases like retinitis pigmentosa or achromatopsia. In this review, we provide an overview of the human diseases and relevant animal models of CNG channelopathies. Furthermore, we summarize recent results from preclinical gene therapy studies using adeno-associated viral vectors and discuss the efficacy and translational potential of these gene therapeutic approaches.

In vivo optophysiology reveals that G-protein activation triggers osmotic swelling and increased light scattering of rod photoreceptors.

PubMed

Zhang, Pengfei; Zawadzki, Robert J; Goswami, Mayank; Nguyen, Phuong T; Yarov-Yarovoy, Vladimir; Burns, Marie E; Pugh, Edward N

2017-04-04

The light responses of rod and cone photoreceptors have been studied electrophysiologically for decades, largely with ex vivo approaches that disrupt the photoreceptors' subretinal microenvironment. Here we report the use of optical coherence tomography (OCT) to measure light-driven signals of rod photoreceptors in vivo. Visible light stimulation over a 200-fold intensity range caused correlated rod outer segment (OS) elongation and increased light scattering in wild-type mice, but not in mice lacking the rod G-protein alpha subunit, transducin (Gα t ), revealing these responses to be triggered by phototransduction. For stimuli that photoactivated one rhodopsin per Gα t the rod OS swelling response reached a saturated elongation of 10.0 ± 2.1%, at a maximum rate of 0.11% s -1 Analyzing swelling as osmotically driven water influx, we find the H 2 O membrane permeability of the rod OS to be (2.6 ± 0.4) × 10 -5 cm⋅s -1 , comparable to that of other cells lacking aquaporin expression. Application of Van't Hoff's law reveals that complete activation of phototransduction generates a potentially harmful 20% increase in OS osmotic pressure. The increased backscattering from the base of the OS is explained by a model combining cytoplasmic swelling, translocation of dissociated G-protein subunits from the disc membranes into the cytoplasm, and a relatively higher H 2 O permeability of nascent discs in the basal rod OS. Translocation of phototransduction components out of the OS may protect rods from osmotic stress, which could be especially harmful in disease conditions that affect rod OS structural integrity.

Redistribution of insoluble interphotoreceptor matrix components during photoreceptor differentiation in the mouse retina.

PubMed

Mieziewska, K; Szél, A; Van Veen, T; Aguirre, G D; Philp, N

1994-07-01

The development of the nervous system is largely influenced by the extracellular matrix (ECM). In the neural retina, the photoreceptors are surrounded by a unique ECM, the interphotoreceptor matrix (IPM). The IPM plays a central and possibly crucial role in the development, maintenance and specific function of the photoreceptors. Therefore, the characterization of IPM components is necessary to understand the mechanisms regulating photoreceptor differentiation. The IPM in the mouse retina was examined during photoreceptor morphogenesis with the monoclonal antibody (MAb) F22, which recognizes a 250 kDa component of the interphotoreceptor matrix. The binding pattern of MAb F22 revealed a striking redistribution in the expression of the 250 kDa F22 antigen in late stage of postnatal photoreceptor differentiation in the mouse retina. The F22 staining was detectable in the IPM around the inner segments on the third postnatal day (P3). The MAb F22 initially labeled the region around inner segments, but as the outer segments elongated, the F22 distribution became concentrated to the matrix around the rod and cone outer segments until P16-17. At P17, the F22 label around rods began to disappear, while the label around cones became more defined. The shift in label distribution was largely completed by P20. Residual rod-associated label disappeared within a few days. In the adult animal, the F22 antibody labeled the cone-associated matrix only, and this labeling pattern remained stationary. The change in the distribution of MAb F22 demonstrated by immunolabeling was not accompanied by changes in the size of the molecule; F22 antigen isolated from the IPM of P13-15, and from adult IPM migrated with the same molecular weight on SDS gels. The distribution of MAb F22 was compared to that of chondroitin sulfate proteoglycans which are abundant in the IPM. The labeling patterns of MAbs CS-56, C6-S and C4-S were distinct from that of MAb F22. A general decrease of the label intensity was seen with two chondroitin sulfate MAbs (CS-56 and C4-S) between 16 days and 4 months, but a total loss of rod-associated label was not observed. All three chondroitin sulfate MAbs labeled the retina at embryonic day (E) 11.5-13.5, a time of outgrowth of ganglion cell axons, but the F22 antigen was not detected in the retina at this stage of development. The results demonstrate that the F22 and the chondroitin sulfate antibodies are recognizing different molecules that have distinct roles in retinal morphogenesis.(ABSTRACT TRUNCATED AT 400 WORDS)

Phosphorylation-independent Suppression of Light-activated Visual Pigment by Arrestin in Carp Rods and Cones*

PubMed Central

Tomizuka, Junko; Tachibanaki, Shuji; Kawamura, Satoru

2015-01-01

Visual pigment in photoreceptors is activated by light. Activated visual pigment (R*) is believed to be inactivated by phosphorylation of R* with subsequent binding of arrestin. There are two types of photoreceptors, rods and cones, in the vertebrate retina, and they express different subtypes of arrestin, rod and cone type. To understand the difference in the function between rod- and cone-type arrestin, we first identified the subtype of arrestins expressed in rods and cones in carp retina. We found that two rod-type arrestins, rArr1 and rArr2, are co-expressed in a rod and that a cone-type arrestin, cArr1, is expressed in blue- and UV-sensitive cones; the other cone-type arrestin, cArr2, is expressed in red- and green-sensitive cones. We quantified each arrestin subtype and estimated its concentration in the outer segment of a rod or a cone in the dark; they were ∼0.25 mm (rArr1 plus rArr2) in a rod and 0.6–0.8 mm (cArr1 or cArr2) in a cone. The effect of each arrestin was examined. In contrast to previous studies, both rod and cone arrestins suppressed the activation of transducin in the absence of visual pigment phosphorylation, and all of the arrestins examined (rArr1, rArr2, and cArr2) bound transiently to most probably nonphosphorylated R*. One rod arrestin, rArr2, bound firmly to phosphorylated pigment, and the other two, rArr1 and cArr2, once bound to phosphorylated R* but dissociated from it during incubation. Our results suggested a novel mechanism of arrestin effect on the suppression of the R* activity in both rods and cones. PMID:25713141

Classical and alternative complement activation on photoreceptor outer segments drives monocyte-dependent retinal atrophy.

PubMed

Katschke, Kenneth J; Xi, Hongkang; Cox, Christian; Truong, Tom; Malato, Yann; Lee, Wyne P; McKenzie, Brent; Arceo, Rommel; Tao, Jianhua; Rangell, Linda; Reichelt, Mike; Diehl, Lauri; Elstrott, Justin; Weimer, Robby M; Campagne, Menno van Lookeren

2018-05-09

Geographic atrophy (GA), the advanced form of dry age-related macular degeneration (AMD), is characterized by progressive loss of retinal pigment epithelium cells and photoreceptors in the setting of characteristic extracellular deposits and remains a serious unmet medical need. While genetic predisposition to AMD is dominated by polymorphisms in complement genes, it remains unclear how complement activation contributes to retinal atrophy. Here we demonstrate that complement is activated on photoreceptor outer segments (POS) in the retina peripheral to atrophic lesions associated with GA. When exposed to human serum following outer blood-retinal barrier breakdown, POS act as potent activators of the classical and alternative complement pathway. In mouse models of retinal degeneration, classical and alternative pathway complement activation on photoreceptors contributed to the loss of photoreceptor function. This was dependent on C5a-mediated recruitment of peripheral blood monocytes but independent of resident microglia. Genetic or pharmacologic inhibition of both classical and alternative complement C3 and C5 convertases was required to reduce progressive degeneration of photoreceptor rods and cones. Our study implicates systemic classical and alternative complement proteins and peripheral blood monocytes as critical effectors of localized retinal degeneration with potential relevance for the contribution of complement activation to GA.

The reduction of retinene1 to vitamina A1 in vitro.

PubMed

WALD, G; HUBBARD, R

1949-01-01

In the surviving vertebrate retina the retinene(1) liberated by bleaching rhodopsin is converted quantitatively to vitamin A(1). Recent chemical studies have indicated that in this process the aldehyde group of retinene(1) is reduced to the primary alcohol group of vitamin A(1) (Morton; Wald). Some time ago we brought this reaction into a cell-free brei prepared from cattle retinas. The retinas were frozen, desiccated, ground, and exhaustively extracted with petroleum ether; the resulting powder, stirred in neutral buffer solution and exposed to light, converted its retinene(1) completely to vitamin A(1). Some time ago also we observed that fresh rhodopsin solutions exhibit a special type of fading in darkness following exposure to light, which is absent from the same solutions after aging. We have confirmed Bliss's identification of this reaction as the conversion of retinene(1) to vitamin A(1). The system which reduces retinene(1) is fractionated anatomically in the retinal rods. The outer segments of the rods, broken off from the underlying retinal tissue, are unable to convert their retinene(1) to vitamin A(1). In the presence of a water extract of crushed retina they do perform this conversion. On the other hand the retinal tissue from which a water extract was taken has lost this capacity. Such washed retinal tissue is reactivated by returning the washings to the solid material. The activating effect of retinal washings on isolated outer limbs or washed retina is duplicated by a boiled muscle juice. This in turn can be replaced by reduced cozymase (reduced coenzyme I; DPN-H(2)); or by a mixture of DPN and fructosediphosphate. The conversion of retinene(1) to vitamin A(1) is therefore a reduction in which two atoms of hydrogen are transferred to retinene(1) from reduced cozymase. It is assumed that this reaction is catalyzed by an apoenzyme, retinene(1) reductase, present in the rod outer limb. This process is coupled with a second system in the outer segment which reduces DPN, using hexosediphosphate or one of its derivatives as hydrogen donor. This action of DPN brings a member of the vitamin B complex, nicotinic acid amide, into an auxiliary position in the rhodopsin system. In the isolated retina or in vitro systems the reduction of retinene(1) proceeds irreversibly. Yet this reduction must be balanced by an oxidative process elsewhere in the rhodopsin cycle, since through rhodopsin as intermediate vitamin A(1) regenerates retinene(1).

Dark adaptation and the retinoid cycle of vision.

PubMed

Lamb, T D; Pugh, E N

2004-05-01

Following exposure of our eye to very intense illumination, we experience a greatly elevated visual threshold, that takes tens of minutes to return completely to normal. The slowness of this phenomenon of "dark adaptation" has been studied for many decades, yet is still not fully understood. Here we review the biochemical and physical processes involved in eliminating the products of light absorption from the photoreceptor outer segment, in recycling the released retinoid to its original isomeric form as 11-cis retinal, and in regenerating the visual pigment rhodopsin. Then we analyse the time-course of three aspects of human dark adaptation: the recovery of psychophysical threshold, the recovery of rod photoreceptor circulating current, and the regeneration of rhodopsin. We begin with normal human subjects, and then analyse the recovery in several retinal disorders, including Oguchi disease, vitamin A deficiency, fundus albipunctatus, Bothnia dystrophy and Stargardt disease. We review a large body of evidence showing that the time-course of human dark adaptation and pigment regeneration is determined by the local concentration of 11-cis retinal, and that after a large bleach the recovery is limited by the rate at which 11-cis retinal is delivered to opsin in the bleached rod outer segments. We present a mathematical model that successfully describes a wide range of results in human and other mammals. The theoretical analysis provides a simple means of estimating the relative concentration of free 11-cis retinal in the retina/RPE, in disorders exhibiting slowed dark adaptation, from analysis of psychophysical measurements of threshold recovery or from analysis of pigment regeneration kinetics.

Mechanically Resilient Polymeric Films Doped with a Lithium Compound

NASA Technical Reports Server (NTRS)

Meador, Mary Ann B. (Inventor); Kinder, James D. (Inventor)

2005-01-01

This invention is a series of mechanically resilient polymeric films, comprising rod-coil block polyimide copolymers, which are doped with a lithium compound providing lithium ion conductivity, that are easy to fabricate into mechanically resilient films with acceptable ionic or protonic conductivity at a variety of temperatures. The copolymers consists of short-rigid polyimide rod segments alternating with polyether coil segments. The rods and coil segments can be linear, branched or mixtures of linear and branched segments. The highly incompatible rods and coil segments phase separate, providing nanoscale channels for ion conduction. The polyimide segments provide dimensional and mechanical stability and can be functionalized in a number of ways to provide specialized functions for a given application. These rod-coil black polyimide copolymers are particularly useful in the preparation of ion conductive membranes for use in the manufacture of fuel cells and lithium based polymer batteries.

In vivo optophysiology reveals that G-protein activation triggers osmotic swelling and increased light scattering of rod photoreceptors

PubMed Central

Nguyen, Phuong T.; Yarov-Yarovoy, Vladimir; Burns, Marie E.; Pugh, Edward N.

2017-01-01

The light responses of rod and cone photoreceptors have been studied electrophysiologically for decades, largely with ex vivo approaches that disrupt the photoreceptors’ subretinal microenvironment. Here we report the use of optical coherence tomography (OCT) to measure light-driven signals of rod photoreceptors in vivo. Visible light stimulation over a 200-fold intensity range caused correlated rod outer segment (OS) elongation and increased light scattering in wild-type mice, but not in mice lacking the rod G-protein alpha subunit, transducin (Gαt), revealing these responses to be triggered by phototransduction. For stimuli that photoactivated one rhodopsin per Gαt the rod OS swelling response reached a saturated elongation of 10.0 ± 2.1%, at a maximum rate of 0.11% s−1. Analyzing swelling as osmotically driven water influx, we find the H2O membrane permeability of the rod OS to be (2.6 ± 0.4) × 10−5 cm⋅s−1, comparable to that of other cells lacking aquaporin expression. Application of Van’t Hoff’s law reveals that complete activation of phototransduction generates a potentially harmful 20% increase in OS osmotic pressure. The increased backscattering from the base of the OS is explained by a model combining cytoplasmic swelling, translocation of dissociated G-protein subunits from the disc membranes into the cytoplasm, and a relatively higher H2O permeability of nascent discs in the basal rod OS. Translocation of phototransduction components out of the OS may protect rods from osmotic stress, which could be especially harmful in disease conditions that affect rod OS structural integrity. PMID:28320964

Photoreceptor Layer Thickness Changes During Dark Adaptation Observed With Ultrahigh-Resolution Optical Coherence Tomography

PubMed Central

Lu, Chen D.; Lee, ByungKun; Schottenhamml, Julia; Maier, Andreas; Pugh, Edward N.; Fujimoto, James G.

2017-01-01

Purpose To examine outer retinal band changes after flash stimulus and subsequent dark adaptation with ultrahigh-resolution optical coherence tomography (UHR-OCT). Methods Five dark-adapted left eyes of five normal subjects were imaged with 3-μm axial-resolution UHR-OCT during 30 minutes of dark adaptation following 96%, 54%, 23%, and 0% full-field and 54% half-field rhodopsin bleach. We identified the ellipsoid zone inner segment/outer segment (EZ[IS/OS]), cone interdigitation zone (CIZ), rod interdigitation zone (RIZ), retinal pigment epithelium (RPE), and Bruch's membrane (BM) axial positions and generated two-dimensional thickness maps of the EZ(IS/OS) to the four bands. The average thickness over an area of the thickness map was compared against that of the dark-adapted baselines. The time-dependent thickness changes (photoresponses) were statistically compared against 0% bleach. Dark adaptometry was performed with the same bleaching protocol. Results The EZ(IS/OS)-CIZ photoresponse was significantly different at 96% (P < 0.0001) and 54% (P = 0.006) bleach. At all three bleaching levels, the EZ(IS/OS)-RIZ, -RPE, and -BM responses were significantly different (P < 0.0001). The EZ(IS/OS)-CIZ and EZ(IS/OS)-RIZ time courses were similar to the recovery of rod- and cone-mediated sensitivity, respectively, measured with dark adaptometry. The maximal EZ(IS/OS)-CIZ and EZ(IS/OS)-RIZ response magnitudes doubled from 54% to 96% bleach. Both EZ(IS/OS)-RPE and EZ(IS/OS)-BM responses resembled dampened oscillations that were graded in amplitude and duration with bleaching intensity. Half-field photoresponses were localized to the stimulated retina. Conclusions With noninvasive, near-infrared UHR-OCT, we characterized three distinct, spatially localized photoresponses in the outer retinal bands. These photoresponses have potential value as physical correlates of photoreceptor function. PMID:28898357

Functional Optical Coherence Tomography Enables In Vivo Physiological Assessment of Retinal Rod and Cone Photoreceptors

PubMed Central

Zhang, Qiuxiang; Lu, Rongwen; Wang, Benquan; Messinger, Jeffrey D.; Curcio, Christine A.; Yao, Xincheng

2015-01-01

Transient intrinsic optical signal (IOS) changes have been observed in retinal photoreceptors, suggesting a unique biomarker for eye disease detection. However, clinical deployment of IOS imaging is challenging due to unclear IOS sources and limited signal-to-noise ratios (SNRs). Here, by developing high spatiotemporal resolution optical coherence tomography (OCT) and applying an adaptive algorithm for IOS processing, we were able to record robust IOSs from single-pass measurements. Transient IOSs, which might reflect an early stage of light phototransduction, are consistently observed in the photoreceptor outer segment almost immediately (<4 ms) after retinal stimulation. Comparative studies of dark- and light-adapted retinas have demonstrated the feasibility of functional OCT mapping of rod and cone photoreceptors, promising a new method for early disease detection and improved treatment of diseases such as age-related macular degeneration (AMD) and other eye diseases that can cause photoreceptor damage. PMID:25901915

The prenyl-binding protein PrBP/δ: a chaperone participating in intracellular trafficking

PubMed Central

Zhang, Houbin; Constantine, Ryan; Frederick, Jeanne M.; Baehr, Wolfgang

2012-01-01

Expressed ubiquitously, PrBP/δ functions as chaperone/co-factor in the transport of a subset of prenylated proteins. PrBP/δ features an immunoglobulin-like β-sandwich fold for lipid binding, and interacts with diverse partners. PrBP/δ binds both C-terminal C15 and C20 prenyl side chains of phototransduction polypeptides and small GTP-binding (G) proteins of the Ras superfamily. PrBP/δ also interacts with the small GTPases, ARL2 and ARL3, which act as release factors (GDFs) for prenylated cargo. Targeted deletion of the mouse Pde6d gene encoding PrBP/δ resulted in impeded trafficking to the outer segments of GRK1 and cone PDE6 which are predicted to be farnesylated and geranylgeranylated, respectively. Rod and cone transducin trafficking was largely unaffected. These trafficking defects produce progressive cone-rod dystrophy in the Pde6d−/− mouse. PMID:22960045

Functional Optical Coherence Tomography Enables In Vivo Physiological Assessment of Retinal Rod and Cone Photoreceptors

NASA Astrophysics Data System (ADS)

Zhang, Qiuxiang; Lu, Rongwen; Wang, Benquan; Messinger, Jeffrey D.; Curcio, Christine A.; Yao, Xincheng

2015-04-01

Transient intrinsic optical signal (IOS) changes have been observed in retinal photoreceptors, suggesting a unique biomarker for eye disease detection. However, clinical deployment of IOS imaging is challenging due to unclear IOS sources and limited signal-to-noise ratios (SNRs). Here, by developing high spatiotemporal resolution optical coherence tomography (OCT) and applying an adaptive algorithm for IOS processing, we were able to record robust IOSs from single-pass measurements. Transient IOSs, which might reflect an early stage of light phototransduction, are consistently observed in the photoreceptor outer segment almost immediately (<4 ms) after retinal stimulation. Comparative studies of dark- and light-adapted retinas have demonstrated the feasibility of functional OCT mapping of rod and cone photoreceptors, promising a new method for early disease detection and improved treatment of diseases such as age-related macular degeneration (AMD) and other eye diseases that can cause photoreceptor damage.

Rod Photopigment Kinetics After Photodisruption of the Retinal Pigment Epithelium

PubMed Central

Masella, Benjamin D.; Hunter, Jennifer J.; Williams, David R.

2014-01-01

Purpose. Advances in retinal imaging have led to the discovery of long-lasting retinal changes caused by light exposures below published safety limits, including disruption of the RPE. To investigate the functional consequences of RPE disruption, we combined adaptive optics ophthalmoscopy with retinal densitometry. Methods. A modified adaptive optics scanning light ophthalmoscope (AOSLO) measured the apparent density and regeneration rate of rhodopsin in two macaques before and after four different 568-nm retinal radiant exposures (RREs; 400–3200 J/cm2). Optical coherence tomography (OCT) was used to measure the optical path length through the photoreceptor outer segments before and after RPE disruption. Results. All tested RREs caused visible RPE disruption. Apparent rhodopsin density was significantly reduced following 1600 (P = 0.01) and 3200 J/cm2 (P = 0.007) exposures. No significant change in apparent density was observed in response to 800 J/cm2. Surprisingly, exposure to 400 J/cm2 showed a significant increase in apparent density (P = 0.047). Rhodopsin recovery rate was not significantly affected by these RREs. Optical coherence tomography measurements showed a significant decrease in the optical path length through the photoreceptor outer segments for RREs above 800 J/cm2 (P < 0.001). Conclusions. At higher RREs, optical path length through the outer segments was reduced. However, the rate of photopigment regeneration was unchanged. While some ambiguity remains as to the correlation between measured reflectivity and absolute rhodopsin density; at the lowest RREs, RPE disruption appears not to be accompanied by a loss of apparent rhodopsin density, which would have been indicative of functional loss. PMID:25316724

26. A typical outer rod room, or rack room, showing ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

26. A typical outer rod room, or rack room, showing the racks for the nine horizontal control rods (HCRs) that would be inserted or withdrawn from the pile to control the rate of reaction. In this case, it is the 105-F Reactor in February 1945. The view is looking away from the pile, which is out of the picture on the left. Several of the cooling water hose reels for the rods can be seen at the end of the racks near the wall. D-8323 - B Reactor, Richland, Benton County, WA

Cone and Rod Loss in Stargardt Disease Revealed by Adaptive Optics Scanning Light Ophthalmoscopy

PubMed Central

Song, Hongxin; Rossi, Ethan A.; Latchney, Lisa; Bessette, Angela; Stone, Edwin; Hunter, Jennifer J.; Williams, David R.; Chung, Mina

2015-01-01

Importance Stargardt disease (STGD1) is characterized by macular atrophy and flecks in the retinal pigment epithelium. The causative ABCA4 gene encodes a protein localizing to photoreceptor outer segments. The pathologic steps by which ABCA4 mutations lead to clinically detectable retinal pigment epithelium changes remain unclear. We investigated early STGD1 using adaptive optics scanning light ophthalmoscopy. Observations Adaptive optics scanning light ophthalmoscopy imaging of 2 brothers with early STGD1 and their unaffected parents was compared with conventional imaging. Cone and rod spacing were increased in both patients (P <.001) with a dark cone appearance. No foveal cones were detected in the older brother. In the younger brother, foveal cones were enlarged with low density (peak cone density, 48.3 × 103 cones/mm2). The ratio of cone to rod spacing was increased in both patients, with greater divergence from normal approaching the foveal center, indicating that cone loss predominates centrally and rod loss increases peripherally. Both parents had normal photoreceptor mosaics. Genetic testing revealed 3 disease-causing mutations. Conclusions and Relevance This study provides in vivo images of rods and cones in STGD1. Although the primary clinical features of STGD1 are retinal pigment epithelial lesions, adaptive optics scanning light ophthalmoscopy reveals increased cone and rod spacing in areas that appear normal in conventional images, suggesting that photoreceptor loss precedes clinically detectable retinal pigment epithelial disease in STGD1. PMID:26247787

Reprogramming metabolism by targeting sirtuin 6 attenuates retinal degeneration

PubMed Central

Zhang, Lijuan; Du, Jianhai; Justus, Sally; Hsu, Chun-Wei; Bonet-Ponce, Luis; Wu, Wen-Hsuan; Tsai, Yi-Ting; Wu, Wei-Pu; Jia, Yading; Duong, Jimmy K.; Mahajan, Vinit B.; Lin, Chyuan-Sheng; Wang, Shuang; Hurley, James B.

2016-01-01

Retinitis pigmentosa (RP) encompasses a diverse group of Mendelian disorders leading to progressive degeneration of rods and then cones. For reasons that remain unclear, diseased RP photoreceptors begin to deteriorate, eventually leading to cell death and, consequently, loss of vision. Here, we have hypothesized that RP associated with mutations in phosphodiesterase-6 (PDE6) provokes a metabolic aberration in rod cells that promotes the pathological consequences of elevated cGMP and Ca2+, which are induced by the Pde6 mutation. Inhibition of sirtuin 6 (SIRT6), a histone deacetylase repressor of glycolytic flux, reprogrammed rods into perpetual glycolysis, thereby driving the accumulation of biosynthetic intermediates, improving outer segment (OS) length, enhancing photoreceptor survival, and preserving vision. In mouse retinae lacking Sirt6, effectors of glycolytic flux were dramatically increased, leading to upregulation of key intermediates in glycolysis, TCA cycle, and glutaminolysis. Both transgenic and AAV2/8 gene therapy–mediated ablation of Sirt6 in rods provided electrophysiological and anatomic rescue of both rod and cone photoreceptors in a preclinical model of RP. Due to the extensive network of downstream effectors of Sirt6, this study motivates further research into the role that these pathways play in retinal degeneration. Because reprogramming metabolism by enhancing glycolysis is not gene specific, this strategy may be applicable to a wide range of neurodegenerative disorders. PMID:27841758

Tissue inhibitor of metalloproteinases 1 enhances rod survival in the rd1 mouse retina.

PubMed

Kim, Hwa Sun; Vargas, Andrew; Eom, Yun Sung; Li, Justin; Yamamoto, Kyra L; Craft, Cheryl Mae; Lee, Eun-Jin

2018-01-01

Retinitis pigmentosa (RP), an inherited retinal degenerative disease, is characterized by a progressive loss of rod photoreceptors followed by loss of cone photoreceptors. Previously, when tissue inhibitor of metalloproteinase 1 (TIMP1), a key extracellular matrix (ECM) regulator that binds to and inhibits activation of Matrix metallopeptidase 9 (MMP9) was intravitreal injected into eyes of a transgenic rhodopsin rat model of RP, S334ter-line3, we discovered cone outer segments are partially protected. In parallel, we reported that a specific MMP9 and MMP2 inhibitor, SB-3CT, interferes with mechanisms leading to rod photoreceptor cell death in an MMP9 dependent manner. Here, we extend our initial rat studies to examine the potential of TIMP1 as a treatment in retinal degeneration by investigating neuroprotective effects in a classic mouse retinal degeneration model, rdPde6b-/- (rd1). The results clearly demonstrate that intravitreal injections of TIMP1 produce extended protection to delay rod photoreceptor cell death. The mean total number of rods in whole-mount retinas was significantly greater in TIMP-treated rd1 retinas (postnatal (P) 30, P35 (P<0.0001) and P45 (P<0.05) than in saline-treated rd1 retinas. In contrast, SB-3CT did not delay rod cell death, leading us to further investigate alternative pathways that do not involve MMPs. In addition to inducing phosphorylated ERK1/2, TIMP1 significantly reduces BAX activity and delays attenuation of the outer nuclear layer (ONL). Physiological responses using scotopic electroretinograms (ERG) reveal b-wave amplitudes from TIMP1-treated retinas are significantly greater than from saline-treated rd1 retinas (P<0.05). In later degenerative stages of rd1 retinas, photopic b-wave amplitudes from TIMP1-treated rd1 retinas are significantly larger than from saline-treated rd1 retinas (P<0.05). Our findings demonstrate that TIMP1 delays photoreceptor cell death. Furthermore, this study provides new insights into how TIMP1 works in the mouse animal model of RP.

Late-onset cone photoreceptor degeneration induced by R172W mutation in Rds and partial rescue by gene supplementation.

PubMed

Conley, Shannon; Nour, May; Fliesler, Steven J; Naash, Muna I

2007-12-01

R172W is a common mutation in the human retinal degeneration slow (RDS) gene, associated with a late-onset dominant macular dystrophy. In this study, the authors characterized a mouse model that closely mimics the human phenotype and tested the feasibility of gene supplementation as a disease treatment strategy. Transgenic mouse lines carrying the R172W mutation were generated. The retinal phenotype associated with this mutation in a low-expresser line (L-R172W) was examined, both structurally (histology with correlative immunohistochemistry) and functionally (electroretinography). By examining animals over time and with various rds genetic backgrounds, the authors evaluated the dominance of the defect. To assess the efficacy of gene transfer therapy as a treatment for this defect, a previously characterized transgenic line expressing the normal mouse peripherin/Rds (NMP) was crossed with a higher-expresser Rds line harboring the R172W mutation (H-R172W). Functional, structural, and biochemical analyses were used to assess rescue of the retinal disease phenotype. In the wild-type (WT) background, L-R172W mice exhibited late-onset (12-month) dominant cone degeneration without any apparent effect on rods. The degeneration was slightly accelerated (9 months) in the rds(+/-) background. L-R172W retinas did not form outer segments in the absence of endogenous Rds. With use of the H-R172W line on an rds(+/-) background for proof-of-principle genetic supplementation studies, the NMP transgene product rescued rod and cone functional defects and supported outer segment integrity up to 3 months of age, but the rescue effect did not persist in older (11-month) animals. The R172W mutation leads to dominant cone degeneration in the mouse model, regardless of the expression level of the transgene. In contrast, effects of the mutation on rods are dose dependent, underscoring the usefulness of the L-R172W line as a faithful model of the human phenotype. This model may prove helpful in future studies on the mechanisms of cone degeneration and for elucidating the different roles of Rds in rods and cones. This study provides evidence that Rds genetic supplementation can be used to partially rescue visual function. Although this strategy is capable of rescuing haploinsufficiency, it does not rescue the long-term degeneration associated with a gain-of-function mutation.

Phosphorylation-independent suppression of light-activated visual pigment by arrestin in carp rods and cones.

PubMed

Tomizuka, Junko; Tachibanaki, Shuji; Kawamura, Satoru

2015-04-10

Visual pigment in photoreceptors is activated by light. Activated visual pigment (R*) is believed to be inactivated by phosphorylation of R* with subsequent binding of arrestin. There are two types of photoreceptors, rods and cones, in the vertebrate retina, and they express different subtypes of arrestin, rod and cone type. To understand the difference in the function between rod- and cone-type arrestin, we first identified the subtype of arrestins expressed in rods and cones in carp retina. We found that two rod-type arrestins, rArr1 and rArr2, are co-expressed in a rod and that a cone-type arrestin, cArr1, is expressed in blue- and UV-sensitive cones; the other cone-type arrestin, cArr2, is expressed in red- and green-sensitive cones. We quantified each arrestin subtype and estimated its concentration in the outer segment of a rod or a cone in the dark; they were ∼0.25 mm (rArr1 plus rArr2) in a rod and 0.6-0.8 mm (cArr1 or cArr2) in a cone. The effect of each arrestin was examined. In contrast to previous studies, both rod and cone arrestins suppressed the activation of transducin in the absence of visual pigment phosphorylation, and all of the arrestins examined (rArr1, rArr2, and cArr2) bound transiently to most probably nonphosphorylated R*. One rod arrestin, rArr2, bound firmly to phosphorylated pigment, and the other two, rArr1 and cArr2, once bound to phosphorylated R* but dissociated from it during incubation. Our results suggested a novel mechanism of arrestin effect on the suppression of the R* activity in both rods and cones. © 2015 by The American Society for Biochemistry and Molecular Biology, Inc.

Crystallization of Proteins from Crude Bovine Rod Outer Segments☆

PubMed Central

Baker, Bo Y.; Gulati, Sahil; Shi, Wuxian; Wang, Benlian; Stewart, Phoebe L.; Palczewski, Krzysztof

2015-01-01

Obtaining protein crystals suitable for X-ray diffraction studies comprises the greatest challenge in the determination of protein crystal structures, especially for membrane proteins and protein complexes. Although high purity has been broadly accepted as one of the most significant requirements for protein crystallization, a recent study of the Escherichia coli proteome showed that many proteins have an inherent propensity to crystallize and do not require a highly homogeneous sample (Totir et al., 2012). As exemplified by RPE65 (Kiser, Golczak, Lodowski, Chance, & Palczewski, 2009), there also are cases of mammalian proteins crystallized from less purified samples. To test whether this phenomenon can be applied more broadly to the study of proteins from higher organisms, we investigated the protein crystallization profile of bovine rod outer segment (ROS) crude extracts. Interestingly, multiple protein crystals readily formed from such extracts, some of them diffracting to high resolution that allowed structural determination. A total of seven proteins were crystallized, one of which was a membrane protein. Successful crystallization of proteins from heterogeneous ROS extracts demonstrates that many mammalian proteins also have an intrinsic propensity to crystallize from complex biological mixtures. By providing an alternative approach to heterologous expression to achieve crystallization, this strategy could be useful for proteins and complexes that are difficult to purify or obtain by recombinant techniques. PMID:25950977

IQCB1 and PDE6B Mutations Cause Similar Early Onset Retinal Degenerations in Two Closely Related Terrier Dog Breeds

PubMed Central

Goldstein, Orly; Mezey, Jason G.; Schweitzer, Peter A.; Boyko, Adam R.; Gao, Chuan; Bustamante, Carlos D.; Jordan, Julie Ann; Aguirre, Gustavo D.; Acland, Gregory M.

2013-01-01

Purpose. To identify the causative mutations in two early-onset canine retinal degenerations, crd1 and crd2, segregating in the American Staffordshire terrier and the Pit Bull Terrier breeds, respectively. Methods. Retinal morphology of crd1- and crd2-affected dogs was evaluated by light microscopy. DNA was extracted from affected and related unaffected controls. Association analysis was undertaken using the Illumina Canine SNP array and PLINK (crd1 study), or the Affymetrix Version 2 Canine array, the “MAGIC” genotype algorithm, and Fisher's Exact test for association (crd2 study). Positional candidate genes were evaluated for each disease. Results. Structural photoreceptor abnormalities were observed in crd1-affected dogs as young as 11-weeks old. Rod and cone inner segment (IS) and outer segments (OS) were abnormal in size, shape, and number. In crd2-affected dogs, rod and cone IS and OS were abnormal as early as 3 weeks of age, progressing with age to severe loss of the OS, and thinning of the outer nuclear layer (ONL) by 12 weeks of age. Genome-wide association study (GWAS) identified association at the telomeric end of CFA3 in crd1-affected dogs and on CFA33 in crd2-affected dogs. Candidate gene evaluation identified a three bases deletion in exon 21 of PDE6B in crd1-affected dogs, and a cytosine insertion in exon 10 of IQCB1 in crd2-affected dogs. Conclusions. Identification of the mutations responsible for these two early-onset retinal degenerations provides new large animal models for comparative disease studies and evaluation of potential therapeutic approaches for the homologous human diseases. PMID:24045995

Membrane attachment is key to protecting transducin GTPase-activating complex from intracellular proteolysis in photoreceptors.

PubMed

Gospe, Sidney M; Baker, Sheila A; Kessler, Christopher; Brucato, Martha F; Winter, Joan R; Burns, Marie E; Arshavsky, Vadim Y

2011-10-12

The members of the R7 regulator of G-protein signaling (RGS) protein subfamily are versatile regulators of G-protein signaling throughout the nervous system. Recent studies indicate that they are often found in complexes with membrane anchor proteins that serve as versatile modulators of their activity, intracellular targeting, and stability. One striking example is the interplay between the membrane anchor R9AP and the RGS9-1 · Gβ5 GTPase-activating complex responsible for the rapid inactivation of the G-protein transducin in vertebrate photoreceptor cells during their recovery from light excitation. The amount of this complex in photoreceptors sets their temporal resolution and is precisely regulated by the expression level of R9AP, which serves to protect the RGS9-1 and Gβ5 subunits from intracellular proteolysis. In this study, we investigated the mechanism by which R9AP performs its protective function in mouse rods and found that it is entirely confined to recruiting RGS9-1 · Gβ5 to cellular membranes. Furthermore, membrane attachment of RGS9-1 · Gβ5 is sufficient for its stable expression in rods even in the absence of R9AP. Our second finding is that RGS9-1 · Gβ5 possesses targeting information that specifies its exclusion from the outer segment and that this information is neutralized by association with R9AP to allow outer segment targeting. Finally, we demonstrate that the ability of R9AP · RGS9-1 · Gβ5 to accelerate GTP hydrolysis on transducin is independent of its means of membrane attachment, since replacing the transmembrane domain of R9AP with a site for lipid modification did not impair the catalytic activity of this complex.

Dual effect of local anesthetics on the function of excitable rod outer segment disk membrane

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mashimo, T.; Abe, K.; Yoshiya, I.

1986-04-01

The effects of local anesthetics and a divalent cation, Ca2+, on the function of rhodopsin were estimated from the measurements of light-induced proton uptake. The light-induced proton uptake by rhodopsin in the rod outer segment disk membrane was enhanced at lower pH (4) but depressed at higher pHs (6 to 8) by the tertiary amine local anesthetics lidocaine, bupivacaine, tetracaine, and dibucaine. The order of local anesthetic-induced depression of the proton uptake followed that of their clinical anesthetic potencies. The depression of the proton uptake versus the concentration of the uncharged form of local anesthetic nearly describes the same curvemore » for small and large dose of added anesthetic. Furthermore, a neutral local anesthetic, benzocaine, depressed the proton uptake at all pHs between 4 and 7. These results indicate that the depression of the proton uptake is due to the effect of only the uncharged form. It is hypothesized that the uncharged form of local anesthetics interacts hydrophobically with the rhodopsin in the disk membrane. The dual effect of local anesthetics on the proton uptake, on the other hand, suggests that the activation of the function of rhodopsin may be caused by the charged form. There was no significant change in the light-induced proton uptake by rhodopsin when 1 mM of Ca2+ was introduced into the disk membrane at varying pHs in the absence or presence of local anesthetics. This fact indicates that Ca2+ ion does not influence the diprotonating process of metarhodopsin; neither does it interfere with the local anesthetic-induced changes in the rhodopsin molecule.« less

Dysfunction of outer segment guanylate cyclase caused by retinal disease related mutations

PubMed Central

Zägel, Patrick; Koch, Karl-Wilhelm

2014-01-01

Membrane bound guanylate cyclases are expressed in rod and cone cells of the vertebrate retina and mutations in several domains of rod outer segment guanylate cyclase 1 (ROS-GC1 encoded by the gene GUCY2D) correlate with different forms of retinal degenerations. In the present work we investigated the biochemical consequences of three point mutations, one is located in position P575L in the juxtamembrane domain close to the kinase homology domain and two are located in the cyclase catalytic domain at H1019P and P1069R. These mutations correlate with various retinal diseases like autosomal dominant progressive cone degeneration, e.g., Leber Congenital Amaurosis and a juvenile form of retinitis pigmentosa. Wildtype and mutant forms of ROS-GC1 were heterologously expressed in HEK cells, their cellular distribution was investigated and activity profiles in the presence and absence of guanylate cyclase-activating proteins were measured. The mutant P575L was active under all tested conditions, but it displayed a twofold shift in the Ca2+-sensitivity, whereas the mutant P1069R remained inactive despite normal expression levels. The mutation H1019P caused the cyclase to become more labile. The different biochemical consequences of these mutations seem to reflect the different clinical symptoms. The mutation P575L induces a dysregulation of the Ca2+-sensitive cyclase activation profile causing a slow progression of the disease by the distortion of the Ca2+-cGMP homeostasis. In contrast, a strong reduction in cGMP synthesis due to an inactive or structurally unstable ROS-GC1 would trigger more severe forms of retinal diseases. PMID:24616660

Differences in the protein composition of bovine retinal rod outer segment disk and plasma membranes isolated by a ricin-gold-dextran density perturbation method

PubMed Central

1987-01-01

The plasma membrane and disk membranes of bovine retinal rod outer segments (ROS) have been purified by a novel density-gradient perturbation method for analysis of their protein compositions. Purified ROS were treated with neuraminidase to expose galactose residues on plasma membrane-specific glycoproteins and labeled with ricin-gold-dextran particles. After the ROS were lysed in hypotonic buffer, the plasma membrane was dissociated from the disks by either mild trypsin digestion or prolonged exposure to low ionic strength buffer. The dense ricin-gold-dextran-labeled plasma membrane was separated from disks by sucrose gradient centrifugation. Electron microscopy was used to follow this fractionation procedure. The dense red pellet primarily consisted of inverted plasma membrane vesicles containing gold particles; the membrane fraction of density 1.13 g/cc consisted of unlabeled intact disks and vesicles. Ricin-binding studies indicated that the plasma membrane from trypsin-treated ROS was purified between 10-15-fold. The protein composition of plasma membranes and disks was significantly different as analyzed by SDS gels and Western blots labeled with lectins and monoclonal antibodies. ROS plasma membrane exhibited three major proteins of 36 (rhodopsin), 38, and 52 kD, three ricin-binding glycoproteins of 230, 160, and 110 kD, and numerous minor proteins in the range of 14-270 kD. In disk membranes rhodopsin appeared as the only major protein. A 220-kD concanavalin A-binding glycoprotein and peripherin, a rim-specific protein, were also present along with minor proteins of 43 and 57-63 kD. Radioimmune assays indicated that the ROS plasma membrane contained about half as much rhodopsin as disk membranes. PMID:2447095

N-retinylidene-phosphatidylethanolamine is the preferred retinoid substrate for the photoreceptor-specific ABC transporter ABCA4 (ABCR).

PubMed

Beharry, Seelochan; Zhong, Ming; Molday, Robert S

2004-12-24

ABCA4, a member of the family of ATP binding cassette (ABC) proteins found in rod and cone photoreceptors, has been implicated in the transport of retinoid compounds across the outer segment disk membrane following the photoactivation of rhodopsin. Mutations in the ABCA4 gene are responsible for Stargardt macular dystrophy and related retinal degenerative diseases that cause a loss in vision. To identify the retinoid substrate that interacts with ABCA4, we have isolated ABCA4 from rod outer segment disk membranes on an immunoaffinity matrix and analyzed retinoid compounds that bind to ABCA4 using high performance liquid chromatography and radiolabeling methods. When all-trans-retinal was added to ABCA4 in the presence of phosphatidylethanolamine, approximately 0.9 mol of N-retinylidene-phosphatidylethanolamine and 0.3 mol of all-trans-retinal were bound per mol of ABCA4 with an apparent K(d) of 2-5 microm. ATP and GTP released these retinoids from ABCA4, whereas ADP, GDP, and nonhydrolyzable derivatives, adenosine 5'-(beta,gamma-imido)triphosphate and guanosine 5'-(beta,gamma-imido)triphosphate, were ineffective. One mole of N-retinyl-phosphatidylethanolamine, the reduced form of N-retinylidene-phosphatidylethanolamine, bound per mol of ABCA4, whereas 0.3 mol of all-trans-retinal were bound in the absence of phosphatidylethanolamine. No binding of all-trans-retinol to ABCA4 was observed. Our results indicate that ABCA4 preferentially binds N-retinylidene-phosphatidylethanolamine with high affinity in the absence of ATP. Our studies further suggest that ATP binding and hydrolysis induces a protein conformational change that causes N-retinylidene-phosphatidylethanolamine to dissociate from ABCA4.

Compact Hybrid Laser Rod and Laser System

NASA Technical Reports Server (NTRS)

Pierrottet, Diego F. (Inventor); Busch, George E. (Inventor); Amzajerdian, Farzin (Inventor)

2017-01-01

A hybrid fiber rod includes a fiber core and inner and outer cladding layers. The core is doped with an active element. The inner cladding layer surrounds the core, and has a refractive index substantially equal to that of the core. The outer cladding layer surrounds the inner cladding layer, and has a refractive index less than that of the core and inner cladding layer. The core length is about 30 to 2000 times the core diameter. A hybrid fiber rod laser system includes an oscillator laser, modulating device, the rod, and pump laser diode(s) energizing the rod from opposite ends. The rod acts as a waveguide for pump radiation but allows for free-space propagation of laser radiation. The rod may be used in a laser resonator. The core length is less than about twice the Rayleigh range. Degradation from single-mode to multi-mode beam propagation is thus avoided.

NUCLEAR REACTOR

DOEpatents

Young, G.

1963-01-01

This patent covers a power-producing nuclear reactor in which fuel rods of slightly enriched U are moderated by heavy water and cooled by liquid metal. The fuel rods arranged parallel to one another in a circle are contained in a large outer closed-end conduit that extends into a tank containing the heavy water. Liquid metal is introduced into the large conduit by a small inner conduit that extends within the circle of fuel rods to a point near the lower closed end of the outer conduit. (AEC) Production Reactors

Morphological Diversity of the Rod Spherule: A Study of Serially Reconstructed Electron Micrographs

PubMed Central

Li, Shuai; Mitchell, Joe; Briggs, Deidrie J.; Young, Jaime K.; Long, Samuel S.; Fuerst, Peter G.

2016-01-01

Purpose Rod spherules are the site of the first synaptic contact in the retina’s rod pathway, linking rods to horizontal and bipolar cells. Rod spherules have been described and characterized through electron micrograph (EM) and other studies, but their morphological diversity related to retinal circuitry and their intracellular structures have not been quantified. Most rod spherules are connected to their soma by an axon, but spherules of rods on the surface of the Mus musculus outer plexiform layer often lack an axon and have a spherule structure that is morphologically distinct from rod spherules connected to their soma by an axon. Retraction of the rod axon and spherule is often observed in disease processes and aging, and the retracted rod spherule superficially resembles rod spherules lacking an axon. We hypothesized that retracted spherules take on an axonless spherule morphology, which may be easier to maintain in a diseased state. To test our hypothesis, we quantified the spatial organization and subcellular structures of rod spherules with and without axons. We then compared them to the retracted spherules in a disease model, mice that overexpress Dscam (Down syndrome cell adhesion molecule), to gain a better understanding of the rod synapse in health and disease. Methods We reconstructed serial EM images of wild type and DscamGoF (gain of function) rod spherules at a resolution of 7 nm in the X-Y axis and 60 nm in the Z axis. Rod spherules with and without axons, and retracted spherules in the DscamGoF retina, were reconstructed. The rod spherule intracellular organelles, the invaginating dendrites of rod bipolar cells and horizontal cell axon tips were also reconstructed for statistical analysis. Results Stereotypical rod (R1) spherules occupy the outer two-thirds of the outer plexiform layer (OPL), where they present as spherical terminals with large mitochondria. This spherule group is highly uniform and composed more than 90% of the rod spherule population. Rod spherules lacking an axon (R2) were also described and characterized. This rod spherule group consists of a specific spatial organization that is strictly located at the apical OPL-facing layer of the Outer Nuclear Layer (ONL). The R2 spherule displays a large bowl-shaped synaptic terminal that hugs the rod soma. Retracted spherules in the DscamGoF retina were also reconstructed to test if they are structurally similar to R2 spherules. The misplaced rod spherules in DscamGoF have a gross morphology that is similar to R2 spherules but have significant disruption in internal synapse organization. Conclusion We described a morphological diversity within Mus musculus rod spherules. This diversity is correlated with rod location in the ONL and contributes to the intracellular differences within spherules. Analysis of the DscamGoF retina indicated that their R2 spherules are not significantly different than wild type R2 spherules, but that their retracted rod spherules have abnormal synaptic organization. PMID:26930660

Morphological Diversity of the Rod Spherule: A Study of Serially Reconstructed Electron Micrographs.

PubMed

Li, Shuai; Mitchell, Joe; Briggs, Deidrie J; Young, Jaime K; Long, Samuel S; Fuerst, Peter G

2016-01-01

Rod spherules are the site of the first synaptic contact in the retina's rod pathway, linking rods to horizontal and bipolar cells. Rod spherules have been described and characterized through electron micrograph (EM) and other studies, but their morphological diversity related to retinal circuitry and their intracellular structures have not been quantified. Most rod spherules are connected to their soma by an axon, but spherules of rods on the surface of the Mus musculus outer plexiform layer often lack an axon and have a spherule structure that is morphologically distinct from rod spherules connected to their soma by an axon. Retraction of the rod axon and spherule is often observed in disease processes and aging, and the retracted rod spherule superficially resembles rod spherules lacking an axon. We hypothesized that retracted spherules take on an axonless spherule morphology, which may be easier to maintain in a diseased state. To test our hypothesis, we quantified the spatial organization and subcellular structures of rod spherules with and without axons. We then compared them to the retracted spherules in a disease model, mice that overexpress Dscam (Down syndrome cell adhesion molecule), to gain a better understanding of the rod synapse in health and disease. We reconstructed serial EM images of wild type and DscamGoF (gain of function) rod spherules at a resolution of 7 nm in the X-Y axis and 60 nm in the Z axis. Rod spherules with and without axons, and retracted spherules in the DscamGoF retina, were reconstructed. The rod spherule intracellular organelles, the invaginating dendrites of rod bipolar cells and horizontal cell axon tips were also reconstructed for statistical analysis. Stereotypical rod (R1) spherules occupy the outer two-thirds of the outer plexiform layer (OPL), where they present as spherical terminals with large mitochondria. This spherule group is highly uniform and composed more than 90% of the rod spherule population. Rod spherules lacking an axon (R2) were also described and characterized. This rod spherule group consists of a specific spatial organization that is strictly located at the apical OPL-facing layer of the Outer Nuclear Layer (ONL). The R2 spherule displays a large bowl-shaped synaptic terminal that hugs the rod soma. Retracted spherules in the DscamGoF retina were also reconstructed to test if they are structurally similar to R2 spherules. The misplaced rod spherules in DscamGoF have a gross morphology that is similar to R2 spherules but have significant disruption in internal synapse organization. We described a morphological diversity within Mus musculus rod spherules. This diversity is correlated with rod location in the ONL and contributes to the intracellular differences within spherules. Analysis of the DscamGoF retina indicated that their R2 spherules are not significantly different than wild type R2 spherules, but that their retracted rod spherules have abnormal synaptic organization.

Vertically-coupled Whispering Gallery Mode Resonator Optical Waveguide, and Methods

NASA Technical Reports Server (NTRS)

Matsko, Andrey B. (Inventor); Savchenkov, Anatolly A. (Inventor); Matleki, Lute (Inventor)

2007-01-01

A vertically-coupled whispering gallery mode (WGM) resonator optical waveguide, a method of reducing a group velocity of light, and a method of making a waveguide are provided. The vertically-coupled WGM waveguide comprises a cylindrical rod portion having a round cross-section and an outer surface. First and second ring-shaped resonators are formed on the outer surface of the cylindrical rod portion and are spaced from each other along a longitudinal direction of the cylindrical rod. The first and second ringshaped resonators are capable of being coupled to each other by way an evanescent field formed in an interior of the cylindrical rod portion.

Probing Mechanisms of Photoreceptor Degeneration in a New Mouse Model of the Common Form of Autosomal Dominant Retinitis Pigmentosa due to P23H Opsin Mutations*♦

PubMed Central

Sakami, Sanae; Maeda, Tadao; Bereta, Grzegorz; Okano, Kiichiro; Golczak, Marcin; Sumaroka, Alexander; Roman, Alejandro J.; Cideciyan, Artur V.; Jacobson, Samuel G.; Palczewski, Krzysztof

2011-01-01

Rhodopsin, the visual pigment mediating vision under dim light, is composed of the apoprotein opsin and the chromophore ligand 11-cis-retinal. A P23H mutation in the opsin gene is one of the most prevalent causes of the human blinding disease, autosomal dominant retinitis pigmentosa. Although P23H cultured cell and transgenic animal models have been developed, there remains controversy over whether they fully mimic the human phenotype; and the exact mechanism by which this mutation leads to photoreceptor cell degeneration remains unknown. By generating P23H opsin knock-in mice, we found that the P23H protein was inadequately glycosylated with levels 1–10% that of wild type opsin. Moreover, the P23H protein failed to accumulate in rod photoreceptor cell endoplasmic reticulum but instead disrupted rod photoreceptor disks. Genetically engineered P23H mice lacking the chromophore showed accelerated photoreceptor cell degeneration. These results indicate that most synthesized P23H protein is degraded, and its retinal cytotoxicity is enhanced by lack of the 11-cis-retinal chromophore during rod outer segment development. PMID:21224384

Membrane current of retinal rods of Caudiverbera caudiverbera (Amphibia: Leptodactylidae): dark noise, spectral and absolute light sensitivity.

PubMed

Palma, F; Roncagliolo, P; Bacigalupo, J; Palacios, A G

2001-01-01

We investigated the photocurrents from isolated rods of the South American anuran, Caudiverbera caudiverbera. Rod outer segments were on average 66.4 +/- 11.2 microm (mean +/- S.D., n = 104) in length and 6.6 +/- 0.9 microm (mean +/- S.D.) in diameter: 40 +/- 22 photoisomerizations (mean +/- S.D., range 10-99, n = 16) were required for eliciting a half-saturating photocurrent response. The time-to-peak was 911 +/- 217 ms (mean +/- S.D., n = 14, 20 degrees C) in the linear range of the response and the integration time of the current response was 1744 +/- 451 ms (mean +/- S.D., n = 14). The time-to-peak appears to be slower and the integration time shorter in Caudiverbera than in Ambystoma tigrinum, Rana pipiens or Xenopus laevis rods under similar experimental conditions. The a-band of rod spectral sensitivity has a lambda(max) at 520 +/- 2.1 nm (mean +/- S.D., range 516-525 nm, n = 24) and the bandwidth fits a porphyropsin visual pigment. The single-event response amplitude ranges from 0.31-0.51 pA, depending on the calculation method. The intrinsic dark current (variance at dark minus variance under bright light) was 0.045 +/- 0.040 pA2 (mean +/- S.D., n = 24). Our results support the presence of a dark-noise component below 1 Hz, with kinetics similar to the single-photon evoked response and a rate of 0.006 events s(-1) (n = 9).

The prenyl-binding protein PrBP/δ: a chaperone participating in intracellular trafficking.

PubMed

Zhang, Houbin; Constantine, Ryan; Frederick, Jeanne M; Baehr, Wolfgang

2012-12-15

Expressed ubiquitously, PrBP/δ functions as chaperone/co-factor in the transport of a subset of prenylated proteins. PrBP/δ features an immunoglobulin-like β-sandwich fold for lipid binding, and interacts with diverse partners. PrBP/δ binds both C-terminal C15 and C20 prenyl side chains of phototransduction polypeptides and small GTP-binding (G) proteins of the Ras superfamily. PrBP/δ also interacts with the small GTPases, ARL2 and ARL3, which act as release factors (GDFs) for prenylated cargo. Targeted deletion of the mouse Pde6d gene encoding PrBP/δ resulted in impeded trafficking to the outer segments of GRK1 and cone PDE6 which are predicted to be farnesylated and geranylgeranylated, respectively. Rod and cone transducin trafficking was largely unaffected. These trafficking defects produce progressive cone-rod dystrophy in the Pde6d(-/-) mouse. Copyright © 2012 Elsevier Ltd. All rights reserved.

The Neural Retina in Retinopathy of Prematurity

PubMed Central

Hansen, Ronald M.; Moskowitz, Anne; Akula, James D.; Fulton, Anne B.

2016-01-01

Retinopathy of prematurity (ROP) is a neurovascular disease that affects prematurely born infants and is known to have significant long term effects on vision. We conducted the studies described herein not only to learn more about vision but also about the pathogenesis of ROP. The coincidence of ROP onset and rapid developmental elongation of the rod photoreceptor outer segments motivated us to consider the role of the rods in this disease. We used noninvasive electroretinographic (ERG), psychophysical, and retinal imaging procedures to study the function and structure of the neurosensory retina. Rod photoreceptor and post-receptor responses are significantly altered years after the preterm days during which ROP is an active disease. The alterations include persistent rod dysfunction, and evidence of compensatory remodeling of the post-receptor retina is found in ERG responses to full-field stimuli and in psychophysical thresholds that probe small retinal regions. In the central retina, both Mild and Severe ROP delay maturation of parafoveal scotopic thresholds and are associated with attenuation of cone mediated multifocal ERG responses, significant thickening of post-receptor retinal laminae, and dysmorphic cone photoreceptors. These results have implications for vision and control of eye growth and refractive development and suggest future research directions. These results also lead to a proposal for noninvasive management using light that may add to the currently invasive therapeutic armamentarium against ROP. PMID:27671171

Modeling the Flexural Rigidity of Rod Photoreceptors

PubMed Central

Haeri, Mohammad; Knox, Barry E.; Ahmadi, Aphrodite

2013-01-01

In vertebrate eyes, the rod photoreceptor has a modified cilium with an extended cylindrical structure specialized for phototransduction called the outer segment (OS). The OS has numerous stacked membrane disks and can bend or break when subjected to mechanical forces. The OS exhibits axial structural variation, with extended bands composed of a few hundred membrane disks whose thickness is diurnally modulated. Using high-resolution confocal microscopy, we have observed OS flexing and disruption in live transgenic Xenopus rods. Based on the experimental observations, we introduce a coarse-grained model of OS mechanical rigidity using elasticity theory, representing the axial OS banding explicitly via a spring-bead model. We calculate a bending stiffness of ∼105 nN⋅μm2, which is seven orders-of-magnitude larger than that of typical cilia and flagella. This bending stiffness has a quadratic relation to OS radius, so that thinner OS have lower fragility. Furthermore, we find that increasing the spatial frequency of axial OS banding decreases OS rigidity, reducing its fragility. Moreover, the model predicts a tendency for OS to break in bands with higher spring number density, analogous to the experimental observation that transgenic rods tended to break preferentially in bands of high fluorescence. We discuss how pathological alterations of disk membrane properties by mutant proteins may lead to increased OS rigidity and thus increased breakage, ultimately contributing to retinal degeneration. PMID:23442852

Gene therapy rescues photoreceptor blindness in dogs and paves the way for treating human X-linked retinitis pigmentosa.

PubMed

Beltran, William A; Cideciyan, Artur V; Lewin, Alfred S; Iwabe, Simone; Khanna, Hemant; Sumaroka, Alexander; Chiodo, Vince A; Fajardo, Diego S; Román, Alejandro J; Deng, Wen-Tao; Swider, Malgorzata; Alemán, Tomas S; Boye, Sanford L; Genini, Sem; Swaroop, Anand; Hauswirth, William W; Jacobson, Samuel G; Aguirre, Gustavo D

2012-02-07

Hereditary retinal blindness is caused by mutations in genes expressed in photoreceptors or retinal pigment epithelium. Gene therapy in mouse and dog models of a primary retinal pigment epithelium disease has already been translated to human clinical trials with encouraging results. Treatment for common primary photoreceptor blindness, however, has not yet moved from proof of concept to the clinic. We evaluated gene augmentation therapy in two blinding canine photoreceptor diseases that model the common X-linked form of retinitis pigmentosa caused by mutations in the retinitis pigmentosa GTPase regulator (RPGR) gene, which encodes a photoreceptor ciliary protein, and provide evidence that the therapy is effective. After subretinal injections of adeno-associated virus-2/5-vectored human RPGR with human IRBP or GRK1 promoters, in vivo imaging showed preserved photoreceptor nuclei and inner/outer segments that were limited to treated areas. Both rod and cone photoreceptor function were greater in treated (three of four) than in control eyes. Histopathology indicated normal photoreceptor structure and reversal of opsin mislocalization in treated areas expressing human RPGR protein in rods and cones. Postreceptoral remodeling was also corrected: there was reversal of bipolar cell dendrite retraction evident with bipolar cell markers and preservation of outer plexiform layer thickness. Efficacy of gene therapy in these large animal models of X-linked retinitis pigmentosa provides a path for translation to human treatment.

Liquid Crystalline Assembly of Coil-Rod-Coil Molecules with Lateral Methyl Groups into 3-D Hexagonal and Tetragonal Assemblies

PubMed Central

Wang, Zhuoshi; Lan, Yu; Zhong, Keli; Liang, Yongri; Chen, Tie; Jin, Long Yi

2014-01-01

In this paper, we report the synthesis and self-assembly behavior of coil-rod-coil molecules, consisting of three biphenyls linked through a vinylene unit as a conjugated rod segment and poly(ethylene oxide) (PEO) with a degree of polymerization (DP) of 7, 12 and 17, incorporating lateral methyl groups between the rod and coil segments as the coil segment. Self-organized investigation of these molecules by means of differential scanning calorimetry (DSC), thermal polarized optical microscopy (POM) and X-ray diffraction (XRD) reveals that the lateral methyl groups attached to the surface of rod and coil segments, dramatically influence the self-assembling behavior in the liquid-crystalline mesophase. Molecule 1 with a relatively short PEO coil length (DP = 7) self-assembles into rectangular and oblique 2-dimensional columnar assemblies, whereas molecules 2 and 3 with DP of 12 and 17 respectively, spontaneously self-organize into unusual 3-dimensional hexagonal close-packed or body-centered tetragonal assemblies. PMID:24699045

Late-Onset Cone Photoreceptor Degeneration Induced by R172W Mutation in Rds and Partial Rescue by Gene Supplementation

PubMed Central

Conley, Shannon; Nour, May; Fliesler, Steven J.; Naash, Muna I.

2008-01-01

Purpose R172W is a common mutation in the human retinal degeneration slow (RDS) gene, associated with a late-onset dominant macular dystrophy. In this study, the authors characterized a mouse model that closely mimics the human phenotype and tested the feasibility of gene supplementation as a disease treatment strategy. Methods Transgenic mouse lines carrying the R172W mutation were generated. The retinal phenotype associated with this mutation in a low-expresser line (L-R172W) was examined, both structurally (histology with correlative immunohistochemistry) and functionally (electroretinography). By examining animals over time and with various rds genetic backgrounds, the authors evaluated the dominance of the defect. To assess the efficacy of gene transfer therapy as a treatment for this defect, a previously characterized transgenic line expressing the normal mouse peripherin/Rds (NMP) was crossed with a higher-expresser Rds line harboring the R172W mutation (H-R172W). Functional, structural, and biochemical analyses were used to assess rescue of the retinal disease phenotype. Results In the wild-type (WT) background, L-R172W mice exhibited late-onset (12-month) dominant cone degeneration without any apparent effect on rods. The degeneration was slightly accelerated (9 months) in the rds+/− background. L-R172W retinas did not form outer segments in the absence of endogenous Rds. With use of the H-R172W line on an rds+/− background for proof-of-principle genetic supplementation studies, the NMP transgene product rescued rod and cone functional defects and supported outer segment integrity up to 3 months of age, but the rescue effect did not persist in older (11-month) animals. Conclusions The R172W mutation leads to dominant cone degeneration in the mouse model, regardless of the expression level of the transgene. In contrast, effects of the mutation on rods are dose dependent, underscoring the usefulness of the L-R172W line as a faithful model of the human phenotype. This model may prove helpful in future studies on the mechanisms of cone degeneration and for elucidating the different roles of Rds in rods and cones. This study provides evidence that Rds genetic supplementation can be used to partially rescue visual function. Although this strategy is capable of rescuing haplo-insufficiency, it does not rescue the long-term degeneration associated with a gain-of-function mutation. PMID:18055786

Force dependence of phagosome trafficking in retinal pigment epithelial cells

NASA Astrophysics Data System (ADS)

Daniel, Rebekah; Koll, Andrew T.; Altman, David

2014-09-01

Retinal pigment epithelial (RPE) cells play an integral role in the renewal of photoreceptor disk membranes. As rod and cone cells shed their outer segments, they are phagocytosed and degraded by the RPE, and a failure in this process can result in retinal degeneration. We have studied the role of myosin VI in nonspecific phagocytosis in a human RPE primary cell line (ARPE-19), testing the hypothesis that this motor generates the forces required to traffic phagosomes in these cells. Experiments were conducted in the presence of forces through the use of in vivo optical trapping. Our results support a role for myosin VI in phagosome trafficking and demonstrate that applied forces modulate rates of phagosome trafficking.

Convergent synthesis of multiporphyrin light-harvesting rods

DOEpatents

Lindsey, Jonathan S.; Loewe, Robert S.

2003-08-05

The present invention provides a convergent method for the synthesis of light harvesting rods. The rods are oligomers of the formula A.sup.1 (A.sup.b+1).sub.b, wherein b is at least 1, A.sup.1 through A.sup.b+1 are covalently coupled rod segments, and each rod segment A.sup.1 through A.sup.1+b comprises a compound of the formula X.sup.1 (X.sup.m+1).sub.m wherein m is at least 1 and X.sup.1 through X.sup.m+1 are covalently coupled porphyrinic macrocycles. Light harvesting arrays and solar cells containing such light harvesting rods are also described, along with intermediates useful in such methods and rods produced by such methods.

RECOVERY OF ROD PHOTORESPONSES IN ABCR-DEFICIENT MICE

PubMed Central

Pawar, Ambarish S.; Qtaishat, Nasser M.; Little, Deborah M.; Pepperberg, David R.

2010-01-01

Purpose ABCR protein in the rod outer segment is thought to facilitate movement of the all-trans retinal photoproduct of rhodopsin bleaching out of the disk lumen. We investigated the extent to which ABCR deficiency affects post-bleach recovery of the rod photoresponse in ABCR-deficient (abcr−/−) mice. Methods Electroretinographic (ERG) a-wave responses were recorded from abcr−/− mice and two control strains. Using a bright probe flash, we examined the course of rod recovery following fractional rhodopsin bleaches of ~10−6, ~3×10−5, ~0.03 and ~0.30–0.40. Results Dark-adapted abcr−/− mice and controls exhibited similar normalized near-peak amplitudes of the paired-flash-ERG-derived, weak-flash response. Response recovery following ~10−6 bleaching exhibited an average exponential time constant of 319, 171 and 213 ms, respectively, in the abcr−/− and the two control strains. Recovery time constants determined for ~3×10−5 bleaching did not differ significantly among strains. However, those determined for the ~0.03 bleach indicated significantly faster recovery in abcr−/− (2.34 ± 0.74 min) than in the controls (5.36 ± 2.20 min, and 5.92 ± 2.44 min). Following ~0.30–0.40 bleaching, the initial recovery in the abcr−/− was on average faster than in controls. Conclusions By comparison with controls, abcr−/− mice exhibit faster rod recovery following a bleach of ~0.03. The data suggest that ABCR in normal rods may directly or indirectly prolong all-trans retinal clearance from the disk lumen over a significant bleaching range, and that the essential function of ABCR may be to promote the clearance of residual amounts of all-trans retinal that remain in the disks long after bleaching. PMID:18263807

Evolutionary Origin of OwlRep, a Megasatellite DNA Associated with Adaptation of Owl Monkeys to Nocturnal Lifestyle

PubMed Central

Nishihara, Hidenori; Stanyon, Roscoe; Kusumi, Junko; Hirai, Hirohisa

2018-01-01

Abstract Rod cells of many nocturnal mammals have a “non-standard” nuclear architecture, which is called the inverted nuclear architecture. Heterochromatin localizes to the central region of the nucleus. This leads to an efficient light transmission to the outer segments of photoreceptors. Rod cells of diurnal mammals have the conventional nuclear architecture. Owl monkeys (genus Aotus) are the only taxon of simian primates that has a nocturnal or cathemeral lifestyle, and this adaptation is widely thought to be secondary. Their rod cells were shown to exhibit an intermediate chromatin distribution: a spherical heterochromatin block was found in the central region of the nucleus although it was less complete than that of typical nocturnal mammals. We recently demonstrated that the primary DNA component of this heterochromatin block was OwlRep, a megasatellite DNA consisting of 187-bp-long repeat units. However, the origin of OwlRep was not known. Here we show that OwlRep was derived from HSAT6, a simple repeat sequence found in the centromere regions of human chromosomes. HSAT6 occurs widely in primates, suggesting that it was already present in the last common ancestor of extant primates. Notably, Strepsirrhini and Tarsiformes apparently carry a single HSAT6 copy, whereas many species of Simiiformes contain multiple copies. Comparison of nucleotide sequences of these copies revealed the entire process of the OwlRep formation. HSAT6, with or without flanking sequences, was segmentally duplicated in New World monkeys. Then, in the owl monkey linage after its divergence from other New World monkeys, a copy of HSAT6 was tandemly amplified, eventually forming a megasatellite DNA. PMID:29294004

BBSome function is required for both the morphogenesis and maintenance of the photoreceptor outer segment

PubMed Central

Hsu, Ying; Kim, Gunhee; Zhang, Qihong; Datta, Poppy; Seo, Seongjin

2017-01-01

Genetic mutations disrupting the structure and function of primary cilia cause various inherited retinal diseases in humans. Bardet-Biedl syndrome (BBS) is a genetically heterogeneous, pleiotropic ciliopathy characterized by retinal degeneration, obesity, postaxial polydactyly, intellectual disability, and genital and renal abnormalities. To gain insight into the mechanisms of retinal degeneration in BBS, we developed a congenital knockout mouse of Bbs8, as well as conditional mouse models in which function of the BBSome (a protein complex that mediates ciliary trafficking) can be temporally inactivated or restored. We demonstrate that BBS mutant mice have defects in retinal outer segment morphogenesis. We further demonstrate that removal of Bbs8 in adult mice affects photoreceptor function and disrupts the structural integrity of the outer segment. Notably, using a mouse model in which a gene trap inhibiting Bbs8 gene expression can be removed by an inducible FLP recombinase, we show that when BBS8 is restored in immature retinas with malformed outer segments, outer segment extension can resume normally and malformed outer segment discs are displaced distally by normal outer segment structures. Over time, the retinas of the rescued mice become morphologically and functionally normal, indicating that there is a window of plasticity when initial retinal outer segment morphogenesis defects can be ameliorated. PMID:29049287

Two-photon excited autofluorescence imaging of freshly isolated frog retinas.

PubMed

Lu, Rong-Wen; Li, Yi-Chao; Ye, Tong; Strang, Christianne; Keyser, Kent; Curcio, Christine A; Yao, Xin-Cheng

2011-06-01

The purpose of this study was to investigate cellular sources of autofluorescence signals in freshly isolated frog (Rana pipiens) retinas. Equipped with an ultrafast laser, a laser scanning two-photon excitation fluorescence microscope was employed for sub-cellular resolution examination of both sliced and flat-mounted retinas. Two-photon imaging of retinal slices revealed autofluorescence signals over multiple functional layers, including the photoreceptor layer (PRL), outer nuclear layer (ONL), outer plexiform layer (OPL), inner nuclear layer (INL), inner plexiform layer (IPL), and ganglion cell layer (GCL). Using flat-mounted retinas, depth-resolved imaging of individual retinal layers further confirmed multiple sources of autofluorescence signals. Cellular structures were clearly observed at the PRL, ONL, INL, and GCL. At the PRL, the autofluorescence was dominantly recorded from the intracellular compartment of the photoreceptors; while mixed intracellular and extracellular autofluorescence signals were observed at the ONL, INL, and GCL. High resolution autofluorescence imaging clearly revealed mosaic organization of rod and cone photoreceptors; and sub-cellular bright autofluorescence spots, which might relate to connecting cilium, was observed in the cone photoreceptors only. Moreover, single-cone and double-cone outer segments could be directly differentiated.

Characterization of photoreceptor degeneration in the rhodopsin P23H transgenic rat line 2 using optical coherence tomography.

PubMed

Monai, Natsuki; Yamauchi, Kodai; Tanabu, Reiko; Gonome, Takayuki; Ishiguro, Sei-Ichi; Nakazawa, Mitsuru

2018-01-01

To characterize the optical coherence tomography (OCT) appearances of photoreceptor degeneration in the rhodopsin P23H transgenic rat (line 2) in relation to the histological, ultrastructural, and electroretinography (ERG) findings. Homozygous rhodopsin P23H transgenic albino rats (line 2, very-slow degeneration model) were employed. Using OCT (Micron IV®; Phoenix Research Labs, Pleasanton, CA, USA), the natural course of photoreceptor degeneration was recorded from postnatal day (P) 15 to P 287. The OCT images were qualitatively observed by comparing them to histological and ultrastructural findings at P 62 and P 169. In addition, each retinal layer was quantitatively analyzed longitudinally during degeneration, compared it to that observed in wild type Sprague-Dawley (SD) rats. The relationships between the ERG (full-field combined rod-cone response, 3.0 cds/m2 stimulation) findings and OCT images were also analyzed. In the qualitative study, the two layers presumably corresponding to the photoreceptor inner segment ellipsoid zone (EZ) and interdigitation zone (IZ) were identified in the P23H rat until PN day 32. However, the photoreceptor inner and outer segment (IS/OS) layer became diffusely hyperreflective on OCT after P 46, and the EZ and IZ zones could no longer be identified on OCT. In contrast, in the SD rats, the EZ and IZ were clearly distinguished until at least P 247. The ultrastructural study showed partial disarrangements of the photoreceptor outer segment discs in the P23H rats at P 62, although a light-microscopic histological study detected almost no abnormality in the outer segment. In the quantitative study, the outer retinal layer including the outer plexiform layer (OPL) and the outer nuclear layer (ONL) became significantly thinner in the P23H rats than in the SD rats after P 71. The thickness of the IS/OS layer was maintained in the P23H rats until P 130, and it became statistically thinner than in the SD rats at P 237. The longitudinal attenuation in the amplitude of the a- and b-waves of ERG was significantly correlated with the thickness of the combined OPL and ONL but not with that of the IS/OS layer. OCT showed the degenerated photoreceptor IS/OS layer in rhodopsin P23H transgenic rats (line 2) as a diffuse hyperreflective zone, even in the early stage, with the partially disarranged and destabilized OS discs recognizable by ultrastructural assessment but not by a histological study. The amplitude of the a- and b-waves mainly depends on the thickness of the OPL and ONL layer rather than the thickness of the photoreceptor IS/OS layer in P23H rats.

Autofluorescence from the outer retina and subretinal space: hypothesis and review.

PubMed

Spaide, Richard

2008-01-01

To review the pathophysiologic principles underlying increased autofluorescence from the outer retina and subretinal space using selected diseases as examples. The ocular imaging information and histopathologic features, when known, were integrated for diseases causing increased autofluorescence from the outer retina and subretinal space. Inferences were taken from this information and used to create a classification scheme. These diseases are principally those that cause separation of the outer retina from the retinal pigment epithelium, thereby preventing proper phagocytosis of photoreceptor outer segments. The separation can arise from increased exudation into the subretinal space or inadequate removal of fluid from the subretinal space. Lack of normal outer segment processing initially leads to increased accumulation of outer segments on the outer retina and subretinal space. Over time, this material is visible as an increasingly thick coating on the outer retina, is yellow, and is autofluorescent. Over time, atrophy develops with thinning of the deposited material and decreasing autofluorescence. The accumulated material is ultimately capable of inducing damage to the retinal pigment epithelium. Diseases causing accumulation of the material include central serous chorioretinopathy, vitelliform macular dystrophy, acute exudative polymorphous vitelliform maculopathy, choroidal tumors, and vitreomacular traction syndrome. The physical separation of the retinal outer segments from the retinal pigment epithelium hinders proper phagocytosis of the outer segments. Accumulation of the shed but not phagocytized outer segments plays a role in disease manifestations for a number of macular diseases.

Guanylate cyclase-activating protein 2 contributes to phototransduction and light adaptation in mouse cone photoreceptors.

PubMed

Vinberg, Frans; Peshenko, Igor V; Chen, Jeannie; Dizhoor, Alexander M; Kefalov, Vladimir J

2018-05-11

Light adaptation of photoreceptor cells is mediated by Ca 2+ -dependent mechanisms. In darkness, Ca 2+ influx through cGMP-gated channels into the outer segment of photoreceptors is balanced by Ca 2+ extrusion via Na + /Ca 2+ , K + exchangers (NCKXs). Light activates a G protein signaling cascade, which closes cGMP-gated channels and decreases Ca 2+ levels in photoreceptor outer segment because of continuing Ca 2+ extrusion by NCKXs. Guanylate cyclase-activating proteins (GCAPs) then up-regulate cGMP synthesis by activating retinal membrane guanylate cyclases (RetGCs) in low Ca 2+ This activation of RetGC accelerates photoresponse recovery and critically contributes to light adaptation of the nighttime rod and daytime cone photoreceptors. In mouse rod photoreceptors, GCAP1 and GCAP2 both contribute to the Ca 2+ -feedback mechanism. In contrast, only GCAP1 appears to modulate RetGC activity in mouse cones because evidence of GCAP2 expression in cones is lacking. Surprisingly, we found that GCAP2 is expressed in cones and can regulate light sensitivity and response kinetics as well as light adaptation of GCAP1-deficient mouse cones. Furthermore, we show that GCAP2 promotes cGMP synthesis and cGMP-gated channel opening in mouse cones exposed to low Ca 2+ Our biochemical model and experiments indicate that GCAP2 significantly contributes to the activation of RetGC1 at low Ca 2+ when GCAP1 is not present. Of note, in WT mouse cones, GCAP1 dominates the regulation of cGMP synthesis. We conclude that, under normal physiological conditions, GCAP1 dominates the regulation of cGMP synthesis in mouse cones, but if its function becomes compromised, GCAP2 contributes to the regulation of phototransduction and light adaptation of cones. © 2018 by The American Society for Biochemistry and Molecular Biology, Inc.

Fuel assembly for the production of tritium in light water reactors

DOEpatents

Cawley, W.E.; Trapp, T.J.

1983-06-10

A nuclear fuel assembly is described for producing tritium in a light water moderated reactor. The assembly consists of two intermeshing arrays of subassemblies. The first subassemblies comprise concentric annular elements of an outer containment tube, an annular target element, an annular fuel element, and an inner neutron spectrums shifting rod. The second subassemblies comprise an outer containment tube and an inner rod of either fuel, target, or neutron spectrum shifting neutral.

Fuel assembly for the production of tritium in light water reactors

DOEpatents

Cawley, William E.; Trapp, Turner J.

1985-01-01

A nuclear fuel assembly is described for producing tritium in a light water moderated reactor. The assembly consists of two intermeshing arrays of subassemblies. The first subassemblies comprise concentric annular elements of an outer containment tube, an annular target element, an annular fuel element, and an inner neutron spectrums shifting rod. The second subassemblies comprise an outer containment tube and an inner rod of either fuel, target, or neutron spectrum shifting neutral.

Protrusion of a rod into the spinal canal 10 years after segmental lumbar spine surgery.

PubMed

Cai, Siyi; Kong, Xiangyi; Yan, Chengrui; Wang, Yipeng; Wan, Xueshuai; Zhang, Jialu; Qiu, Guixing; Yu, Keyi

2017-03-01

The objective of this article is to report an unusual case of a spinal rod that protruded into the spinal canal after lumbar spine surgery.Only 4 cases of spinal rod migration with protrusion into the spinal canal have been reported. This is the first report of a case involving the use of posterior low lumbar segmental instrumentation with a screw-rod system. The left side of the rod gradually migrated and finally protruded into the canal and compressed the cord.A 60-year-old woman presented with pain and numbness of the posterior aspect of the left leg after a long-distance walk. Intermittent claudication became worse, and she developed pain and numbness in the perineal region. An x-ray showed that the left side of a spinal rod among the segmental spinal instruments that had been placed 10 years previously had protruded into the spinal canal.We removed the rod and decompressed the canal at the level of L5-S1. The patient became totally asymptomatic.Rods used as spinal instrumentation have the possibility of protruding into the spinal canal and endangering the nervous system. Long-term follow-up with radiological examinations should be conducted upon completion of spinal operations conducting using instrumentation.

Physical insight into light scattering by photoreceptor cell nuclei.

PubMed

Kreysing, Moritz; Boyde, Lars; Guck, Jochen; Chalut, Kevin J

2010-08-01

A recent study showed that the rod photoreceptor cell nuclei in the retina of nocturnal and diurnal mammals differ considerably in architecture: the location of euchromatin and heterochromatin in the nucleus is interchanged. This inversion has significant implications for the refractive index distribution and the light scattering properties of the nucleus. Here, we extend previous two-dimensional analysis to three dimensions (3D) by using both a numerical finite-difference time-domain and an analytic Mie theory approach. We find that the specific arrangement of the chromatin phases in the nuclear core-shell models employed have little impact on the far-field scattering cross section. However, scattering in the near field, which is the relevant regime inside the retina, shows a significant difference between the two architectures. The "inverted" photoreceptor cell nuclei of nocturnal mammals act as collection lenses, with the lensing effect being much more pronounced in 3D than in two dimensions. This lensing helps to deliver light efficiently to the light-sensing outer segments of the rod photoreceptor cells and thereby improve night vision.

Planar torsion spring

NASA Technical Reports Server (NTRS)

Ihrke, Chris A. (Inventor); Parsons, Adam H. (Inventor); Mehling, Joshua S. (Inventor); Griffith, Bryan Kristian (Inventor)

2012-01-01

A torsion spring comprises an inner mounting segment. An outer mounting segment is located concentrically around the inner mounting segment. A plurality of splines extends from the inner mounting segment to the outer mounting segment. At least a portion of each spline extends generally annularly around the inner mounting segment.

LONG-TERM SD-OCT/SLO IMAGING OF NEURORETINA AND RETINAL PIGMENT EPITHELIUM AFTER SUB-THRESHOLD INFRARED LASER TREATMENT OF DRUSEN

PubMed Central

MOJANA, FRANCESCA; BRAR, MANPREET; CHENG, LINGYUN; BARTSCH, DIRK-UWE G.; FREEMAN, WILLIAM R.

2012-01-01

PURPOSE To determine the long-term effect of sub-threshold diode laser treatment for drusen in patients with non-exudative age-related macular degeneration (AMD) with spectral domain optical coherence tomography combined with simultaneous scanning laser ophthalmoscope (SD-OCT/SLO). METHODS 8 eyes of 4 consecutive AMD patients with bilateral drusen previously treated with sub-threshold diode laser were imaged with SD-OCT/SLO. Abnormalities in the outer retina layers reflectivity as seen with SD-OCT/SLO were retrospectively analyzed and compared with color fundus pictures and autofluorescence images (AF) acquired immediately before and after the laser treatment. RESULTS A focal discrete disruptions in the reflectivity of the outer retinal layers was noted in 29% of the laser lesions. The junction in between the inner and outer segment of the photoreceptor was more frequently affected, with associated focal damage of the outer nuclear layer. Defects of the RPE were occasionally detected. These changes did not correspond to threshold burns on color fundus photography, but corresponded to focal areas of increased AF in the majority of the cases. CONCLUSIONS Sub-threshold diode laser treatment causes long-term disruption of the retinal photoreceptor layer as analyzed by SD-OCT/SLO. The concept that sub-threshold laser treatment can achieve a selected RPE effect without damage to rods and cones may be flawed. PMID:21157398

Light regulation of the insulin receptor in the retina.

PubMed

Rajala, Raju V S; Anderson, Robert E

2003-10-01

The peptide hormone insulin binds its cognate cell-surface receptors to activate a coordinated biochemical-signaling network and to induce intracellular events. The retina is an integral part of the central nervous system and is known to contain insulin receptors, although their function is unknown. This article, describes recent studies that link the photobleaching of rhodopsin to tyrosine phosphorylation of the insulin receptor and subsequent activation of phosphoinositide 3- kinase (PI3K). We recently found a light-dependent increase in tyrosine phosphorylation of the insulin receptor-beta-subunit (IR beta) and an increase in PI3K enzyme activity in isolated rod outer segments (ROS) and in anti-phosphotyrosine (PY) and anti-IR beta immunoprecipitates of retinal homogenates. The light effect, which was localized to photoreceptor neurons, is independent of insulin secretion. Our results suggest that light induces tyrosine phosphorylation of IR beta in outer-segment membranes, which leads to the binding of p85 through its N-terminal SH2 domain and the generation of PI-3,4,5-P3. We suggest that the physiological role of this process may be to provide neuroprotection of the retina against light damage by activating proteins that protect against stress-induced apoptosis. The studies linking PI3K activation through tyrosine phosphorylation of IR beta now provide physiological relevance for the presence of these receptors in the retina.

Phototransduction early steps model based on Beer-Lambert optical law.

PubMed

Salido, Ezequiel M; Servalli, Leonardo N; Gomez, Juan Carlos; Verrastro, Claudio

2017-02-01

The amount of available rhodopsin on the photoreceptor outer segment and its change over time is not considered in classic models of phototransduction. Thus, those models do not take into account the absorptance variation of the outer segment under different brightness conditions. The relationship between the light absorbed by a medium and its absorptance is well described by the Beer-Lambert law. This newly proposed model implements the absorptance variation phenomenon in a set of equations that admit photons per second as input and results in active rhodopsins per second as output. This study compares the classic model of phototransduction developed by Forti et al. (1989) to this new model by using different light stimuli to measure active rhodopsin and photocurrent. The results show a linear relationship between light stimulus and active rhodopsin in the Forti model and an exponential saturation in the new model. Further, photocurrent values have shown that the new model behaves equivalently to the experimental and theoretical data as published by Forti in dark-adapted rods, but fits significantly better under light-adapted conditions. The new model successfully introduced a physics optical law to the standard model of phototransduction adding a new processing layer that had not been mathematically implemented before. In addition, it describes the physiological concept of saturation and delivers outputs in concordance to input magnitudes. Copyright © 2017 Elsevier Ltd. All rights reserved.

Detailed functional and structural phenotype of Bietti crystalline dystrophy associated with mutations in CYP4V2 complicated by choroidal neovascularization.

PubMed

Fuerst, Nicole M; Serrano, Leona; Han, Grace; Morgan, Jessica I W; Maguire, Albert M; Leroy, Bart P; Kim, Benjamin J; Aleman, Tomas S

2016-12-01

To describe in detail the phenotype of a patient with Bietti crystalline dystrophy (BCD) complicated by choroidal neovascularization (CNV) and the response to intravitreal Bevacizumab (Avastin ® ; Genentech/Roche). A 34-year-old woman with BCD and mutations in CYP4V2 (c.802-8_806del13/p.H331P:c992A>C) underwent a complete ophthalmic examination, full-field flash electroretinography (ERG), kinetic and two-color dark-adapted perimetry, and dark-adaptometry. Imaging was performed with spectral domain optical coherence tomography (SD-OCT), near infrared (NIR) and short wavelength (SW) fundus autofluorescence (FAF), and fluorescein angiography (FA). Best-corrected visual acuity (BCVA) was 20/20 and 20/60 for the right and left eye, respectively. There were corneal paralimbal crystal-like deposits. Kinetic fields were normal in the peripheral extent. Retinal crystals were most obvious on NIR-reflectance and corresponded with hyperreflectivities within the RPE on SD-OCT. There was parafoveal/perifoveal hypofluorescence on SW-FAF and NIR-FAF. Rod > cone sensitivity loss surrounded fixation and extended to ~10° of eccentricity corresponding to regions of photoreceptor outer segment-retinal pigmented epithelium (RPE) interdigitation abnormalities. The outer nuclear layer was normal in thickness. Recovery of sensitivity following a ~76% rhodopsin bleach was normal. ERGs were normal. A subretinal hemorrhage in the left eye co-localized with elevation of the RPE on SD-OCT and leakage on FA, suggestive of CNV. Three monthly intravitreal injections of Bevacizumab led to restoration of BCVA to baseline (20/25). crystals in BCD were predominantly located within the RPE. Photoreceptor outer segment and apical RPE abnormalities underlie the relatively extensive retinal dysfunction observed in relatively early-stage BCD. Intravitreal Bevacizumab was effective in treating CNV in this setting.

Layered reactive particles with controlled geometries, energies, and reactivities, and methods for making the same

DOEpatents

Fritz, Gregory M.; Weihs, Timothy P.; Grzyb, Justin A.

2016-07-05

An energetic composite having a plurality of reactive particles each having a reactive multilayer construction formed by successively depositing reactive layers on a rod-shaped substrate having a longitudinal axis, dividing the reactive-layer-deposited rod-shaped substrate into a plurality of substantially uniform longitudinal segments, and removing the rod-shaped substrate from the longitudinal segments, so that the reactive particles have a controlled, substantially uniform, cylindrically curved or otherwise rod-contoured geometry which facilitates handling and improves its packing fraction, while the reactant multilayer construction controls the stability, reactivity and energy density of the energetic composite.

Layered reactive particles with controlled geometries, energies, and reactivities, and methods for making the same

DOEpatents

Fritz, Gregory M; Knepper, Robert Allen; Weihs, Timothy P; Gash, Alexander E; Sze, John S

2013-04-30

An energetic composite having a plurality of reactive particles each having a reactive multilayer construction formed by successively depositing reactive layers on a rod-shaped substrate having a longitudinal axis, dividing the reactive-layer-deposited rod-shaped substrate into a plurality of substantially uniform longitudinal segments, and removing the rod-shaped substrate from the longitudinal segments, so that the reactive particles have a controlled, substantially uniform, cylindrically curved or otherwise rod-contoured geometry which facilitates handling and improves its packing fraction, while the reactant multilayer construction controls the stability, reactivity and energy density of the energetic composite.

En face spectral domain optical coherence tomography analysis of lamellar macular holes.

PubMed

Clamp, Michael F; Wilkes, Geoff; Leis, Laura S; McDonald, H Richard; Johnson, Robert N; Jumper, J Michael; Fu, Arthur D; Cunningham, Emmett T; Stewart, Paul J; Haug, Sara J; Lujan, Brandon J

2014-07-01

To analyze the anatomical characteristics of lamellar macular holes using cross-sectional and en face spectral domain optical coherence tomography. Forty-two lamellar macular holes were retrospectively identified for analysis. The location, cross-sectional length, and area of lamellar holes were measured using B-scans and en face imaging. The presence of photoreceptor inner segment/outer segment disruption and the presence or absence of epiretinal membrane formation were recorded. Forty-two lamellar macular holes were identified. Intraretinal splitting occurred within the outer plexiform layer in 97.6% of eyes. The area of intraretinal splitting in lamellar holes did not correlate with visual acuity. Eyes with inner segment/outer segment disruption had significantly worse mean logMAR visual acuity (0.363 ± 0.169; Snellen = 20/46) than in eyes without inner segment/outer segment disruption (0.203 ± 0.124; Snellen = 20/32) (analysis of variance, P = 0.004). Epiretinal membrane was present in 34 of 42 eyes (81.0%). En face imaging allowed for consistent detection and quantification of intraretinal splitting within the outer plexiform layer in patients with lamellar macular holes, supporting the notion that an area of anatomical weakness exists within Henle's fiber layer, presumably at the synaptic connection of these fibers within the outer plexiform layer. However, the en face area of intraretinal splitting did not correlate with visual acuity, disruption of the inner segment/outer segment junction was associated with significantly worse visual acuity in patients with lamellar macular holes.

The limit of photoreceptor sensitivity: molecular mechanisms of dark noise in retinal cones.

PubMed

Holcman, David; Korenbrot, Juan I

2005-06-01

Detection threshold in cone photoreceptors requires the simultaneous absorption of several photons because single photon photocurrent is small in amplitude and does not exceed intrinsic fluctuations in the outer segment dark current (dark noise). To understand the mechanisms that limit light sensitivity, we characterized the molecular origin of dark noise in intact, isolated bass single cones. Dark noise is caused by continuous fluctuations in the cytoplasmic concentrations of both cGMP and Ca(2+) that arise from the activity in darkness of both guanylate cyclase (GC), the enzyme that synthesizes cGMP, and phosphodiesterase (PDE), the enzyme that hydrolyzes it. In cones loaded with high concentration Ca(2+) buffering agents, we demonstrate that variation in cGMP levels arise from fluctuations in the mean PDE enzymatic activity. The rates of PDE activation and inactivation determine the quantitative characteristics of the dark noise power density spectrum. We developed a mathematical model based on the dynamics of PDE activity that accurately predicts this power spectrum. Analysis of the experimental data with the theoretical model allows us to determine the rates of PDE activation and deactivation in the intact photoreceptor. In fish cones, the mean lifetime of active PDE at room temperature is approximately 55 ms. In nonmammalian rods, in contrast, active PDE lifetime is approximately 555 ms. This remarkable difference helps explain why cones are noisier than rods and why cone photocurrents are smaller in peak amplitude and faster in time course than those in rods. Both these features make cones less light sensitive than rods.

Hidden contributions of the enamel rods on the fracture resistance of human teeth

PubMed Central

Yahyazadehfar, M.; Bajaj, Devendra; Arola, Dwayne D.

2013-01-01

The enamel of human teeth is generally regarded as a brittle material with low fracture toughness. Consequently, the contributions of this tissue in resisting tooth fracture and the importance of its complex microstructure have been largely overlooked. In this study an experimental evaluation of the crack growth resistance of human enamel was conducted to characterize the role of rod (i.e. prism) orientation and degree of decussation on the fracture behavior of this tissue. Incremental crack growth was achieved in-plane, with the rods in directions longitudinal or transverse to their axes. Results showed that the fracture resistance of enamel is both inhomogeneous and spatially anisotropic. Cracks extending transverse to the rods in the outer enamel undergo a lower rise in toughness with extension, and achieve significantly lower fracture resistance than in the longitudinal direction. Though cracks initiating at the surface of teeth may begin extension towards the dentin–enamel junction, they are deflected by the decussated rods and continue growth about the tooth’s periphery, transverse to the rods in the outer enamel. This process facilitates dissipation of fracture energy and averts cracks from extending towards the dentin and vital pulp. PMID:23022547

High-Speed Ultra-High-Resolution Optical Coherence Tomography Findings in Hydroxychloroquine Retinopathy

PubMed Central

Rodriguez-Padilla, Julio A.; Hedges, Thomas R.; Monson, Bryan; Srinivasan, Vivek; Wojtkowski, Maciej; Reichel, Elias; Duker, Jay S.; Schuman, Joel S.; Fujimoto, James G.

2007-01-01

Objectives To compare structural changes in the retina seen on high-speed ultra–high-resolution optical coherence tomography (hsUHR-OCT) with multifocal electroretinography (mfERG) and automated visual fields in patients receiving hydroxychloroquine. Methods Fifteen patients receiving hydroxychloroquine were evaluated clinically with hsUHR-OCT, mfERG, and automated visual fields. Six age-matched subjects were imaged with hsUHR-OCT and served as controls. Results Distinctive discontinuity of the perifoveal photoreceptor inner segment/outer segment junction and thinning of the outer nuclear layer were seen with hsUHR-OCT in patients with mild retinal toxic effects. Progression to complete loss of the inner segment/outer segment junction and hyperscattering at the outer segment level were seen in more advanced cases. The mfERG abnormalities correlated with the hsUHR-OCT findings. Asymptomatic patients had normal hsUHR-OCT and mfERG results. Conclusion Distinctive abnormalities in the perifoveal photoreceptor inner segment/outer segment junction were seen on hsUHR-OCT in patients receiving hydroxychloroquine who also were symptomatic and had abnormalities on automated visual fields and mfERG. PMID:17562988

Effect of Branching on Rod-coil Polyimides as Membrane Materials for Lithium Polymer Batteries

NASA Technical Reports Server (NTRS)

Meador, Mary Ann B.; Cubon, Valerie A.; Scheiman, Daniel A.; Bennett, William R.

2003-01-01

This paper describes a series of rod-coil block co-polymers that produce easy to fabricate, dimensionally stable films with good ionic conductivity down to room temperature for use as electrolytes for lithium polymer batteries. The polymers consist of short, rigid rod polyimide segments, alternating with flexible, polyalkylene oxide coil segments. The highly incompatible rods and coils should phase separate, especially in the presence of lithium ions. The coil phase would allow for conduction of lithium ions, while the rigid rod phase would provide a high degree of dimensional stability. An optimization study was carried out to study the effect of four variables (degree of branching, formulated molecular weight, polymerization solvent and lithium salt concentration) on ionic conductivity, glass transition temperature and dimensional stability in this system.

Molecular Characterization of abLIM, a Novel Actin-binding and Double Zinc Finger Protein

PubMed Central

Roof, Dorothy J.; Hayes, Annmarie; Adamian, Michael; Chishti, Athar H.; Li, Tiansen

1997-01-01

Molecules that couple the actin-based cytoskeleton to intracellular signaling pathways are central to the processes of cellular morphogenesis and differentiation. We have characterized a novel protein, the actin-binding LIM (abLIM) protein, which could mediate such interactions between actin filaments and cytoplasmic targets. abLIM protein consists of a COOH-terminal cytoskeletal domain that is fused to an NH2-terminal domain consisting of four double zinc finger motifs. The cytoskeletal domain is ∼50% identical to erythrocyte dematin, an actin-bundling protein of the red cell membrane skeleton, while the zinc finger domains conform to the LIM motif consensus sequence. In vitro expression studies demonstrate that abLIM protein can bind to F-actin through the dematin-like domain. Transcripts corresponding to three distinct isoforms have a widespread tissue distribution. However, a polypeptide corresponding to the full-length isoform is found exclusively in the retina and is enriched in biochemical extracts of retinal rod inner segments. abLIM protein also undergoes extensive phosphorylation in light-adapted retinas in vivo, and its developmental expression in the retina coincides with the elaboration of photoreceptor inner and outer segments. Based on the composite primary structure of abLIM protein, actin-binding capacity, potential regulation via phosphorylation, and isoform expression pattern, we speculate that abLIM may play a general role in bridging the actin-based cytoskeleton with an array of potential LIM protein-binding partners. The developmental time course of abLIM expression in the retina suggests that the retina-specific isoform may have a specialized role in the development or elaboration of photoreceptor inner and outer segments. PMID:9245787

Localization of visual pigment antigens to photoreceptor cells with different oil droplets in the chicken retina.

PubMed

Szél, A; Röhlich, P

1985-01-01

Frozen semithin sections and unembedded retinal pieces were investigated by immunocytochemistry using two antibodies produced against visual pigments in our laboratory. One was a polyclonal serum (AO) raised against bovine rhodopsin, while the other one was a monoclonal antibody (COS-1) produced against an epitope present in a cone visual pigment. AO stained, as expected, rod outer segments; in addition it also recognized a single cone characterized by a deep yellow oil droplet as well as another single cone with a yellowish green oil droplet. In contrast, COS-1 labelled both members of the double cones; the principal member having a yellowish-green oil droplet and the accessory member. COS-1 also stained a single cone type exhibiting a large red oil droplet.

Pore forming properties of cecropin-melittin hybrid peptide in a natural membrane.

PubMed

Milani, Alberto; Benedusi, Mascia; Aquila, Marco; Rispoli, Giorgio

2009-12-11

The pore forming properties of synthetic cecropin-melittin hybrid peptide (Acetyl-KWKLFKKIGAVLKVL-CONH(2); CM15) were investigated by using photoreceptor rod outer segments (OS) isolated from frog retinae obtained by using the whole-cell configuration of the patch-clamp technique. CM15 was applied (and removed) to (from) the OS in approximately 50 ms with a computer-controlled microperfusion system. Once the main OS endogenous conductance was blocked with light, the OS membrane resistance was >or=1 G Omega, allowing high resolution, low-noise recordings. Different to alamethicines, CM15 produced voltage-independent membrane permeabilisation, repetitive peptide application caused a progressive permeabilisation increase, and no single-channel events were detected at low peptide concentrations. Collectively, these results indicate a toroidal mechanism of pore formation by CM15.

A FRAP-Based Method for Monitoring Molecular Transport in Ciliary Photoreceptor Cells In Vivo.

PubMed

Wunderlich, Kirsten A; Wolfrum, Uwe

2016-01-01

The outer segment of rod and cone photoreceptor cells represents a highly modified primary sensory cilium. It renews on a daily basis throughout lifetime and effective vectorial transport to the cilium is essential for the maintenance of the photoreceptor cell function. Defects in molecules of transport modules lead to severe retinal ciliopathies. We have recently established a fluorescence recovery after photobleaching (FRAP)-based method to monitor molecular trafficking in living rodent photoreceptor cells. We irreversibly bleach the fluorescence of tagged molecules (e.g. eGFP-Rhodopsin) in photoreceptor cells of native vibratome sections through the retina by high laser intensity. In the laser scanning microscope, the recovery of the fluorescent signal is monitored over time and the kinetics of movements of molecules can be quantitatively ascertained.

KCNQ5/Kv7.5 potassium channel expression and subcellular localization in primate retinal pigment epithelium and neural retina

PubMed Central

Zhang, Xiaoming; Yang, Dongli

2011-01-01

Previous studies identified in retinal pigment epithelial (RPE) cells an M-type K+ current, which in many other cell types is mediated by channels encoded by KCNQ genes. The aim of this study was to assess the expression of KCNQ genes in the monkey RPE and neural retina. Application of the specific KCNQ channel blocker XE991 eliminated the M-type current in freshly isolated monkey RPE cells, indicating that KCNQ subunits contribute to the underlying channels. RT-PCR analysis revealed the expression of KCNQ1, KCNQ4, and KCNQ5 transcripts in the RPE and all five KCNQ transcripts in the neural retina. At the protein level, KCNQ5 was detected in the RPE, whereas both KCNQ4 and KCNQ5 were found in neural retina. In situ hybridization in frozen monkey retinal sections revealed KCNQ5 gene expression in the ganglion cell layer and the inner and outer nuclear layers of the neural retina, but results in the RPE were inconclusive due to the presence of melanin. Immunohistochemistry revealed KCNQ5 in the inner and outer plexiform layers, in cone and rod photoreceptor inner segments, and near the basal membrane of the RPE. The data suggest that KCNQ5 channels contribute to the RPE basal membrane K+ conductance and, thus, likely play an important role in active K+ absorption. The distribution of KCNQ5 in neural retina suggests that these channels may function in the shaping of the photoresponses of cone and rod photoreceptors and the processing of visual information by retinal neurons. PMID:21795522

Ceramic-metal composite article and joining method

DOEpatents

Kang, Shinhoo; Selverian, John H.; Kim, Hans J.; Dunn, Edmund M.; Kim, Kyung S.

1992-01-01

A ceramic-metal article including a ceramic rod, a metal rod, and a braze joining the ceramic and metal rods at a braze area of a coaxial bore in the metal rod. The bore gradually decreases in diameter, having an inward seat area sized for close sliding fit about the ceramic, a larger brazing area near the joint end, and a void area intermediate the braze and seat areas. The ceramic is seated without brazing in the bore seat area. The side wall between the brazing area and the metal outer surface is about 0.030-0.080 inch. The braze includes an inner braze layer, an outer braze layer, and an interlayer about 0.030-0.090 inch thick. A shoulder between the brazing and void areas supports the interlayer during bonding while preventing bonding between the void area and the ceramic member, leaving a void space between the void area and the ceramic member. A venting orifice extends generally radially through the metal member from the outer surface to the void space. The braze layers are palladium, platinum, gold, silver, copper, nickel, indium, chromium, molybdenum, niobium, iron, aluminum, or alloys thereof. Preferred is a gold-palladium-nickel brazing alloy. The interlayer is nickel, molybdenum, copper, tantalum, tungsten, niobium, aluminum, cobalt, iron, or an alloy thereof.

Ceramic-metal composite article and joining method

DOEpatents

Kang, S.; Selverian, J.H.; Kim, H.J.; Dunn, E.M.; Kim, K.S.

1992-04-28

A ceramic-metal article including a ceramic rod, a metal rod, and a braze joining the ceramic and metal rods at a braze area of a coaxial bore in the metal rod is described. The bore gradually decreases in diameter, having an inward seat area sized for close sliding fit about the ceramic, a larger brazing area near the joint end, and a void area intermediate the braze and seat areas. The ceramic is seated without brazing in the bore seat area. The side wall between the brazing area and the metal outer surface is about 0.030-0.080 inch. The braze includes an inner braze layer, an outer braze layer, and an interlayer about 0.030-0.090 inch thick. A shoulder between the brazing and void areas supports the interlayer during bonding while preventing bonding between the void area and the ceramic member, leaving a void space between the void area and the ceramic member. A venting orifice extends generally radially through the metal member from the outer surface to the void space. The braze layers are palladium, platinum, gold, silver, copper, nickel, indium, chromium, molybdenum, niobium, iron, aluminum, or alloys thereof. Preferred is a gold-palladium-nickel brazing alloy. The interlayer is nickel, molybdenum, copper, tantalum, tungsten, niobium, aluminum, cobalt, iron, or an alloy thereof. 4 figs.

High frequency magnetostrictive transducers for waveguide applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Daw, Joshua Earl; Taylor, Steven Cheney; Rempe, Joy Lynn

A high frequency magnetostrictive transducer includes a magnetostrictive rod or wire inserted co-axially into a driving coil, wherein the driving coil includes a coil arrangement with a plurality of small coil segments along the magnetostrictive rod or wire; wherein frequency operation of the high frequency magnetostrictive transducer is controlled by a length of the small coil segments and a material type of the magnetostrictive rod or wire. This design of the high frequency magnetostrictive transducer retains the beneficial aspects of the magnetostrictive design, while reducing its primary drawback, lower frequency operation.

Natural History of the Central Structural Abnormalities in Choroideremia: A Prospective Cross-Sectional Study.

PubMed

Aleman, Tomas S; Han, Grace; Serrano, Leona W; Fuerst, Nicole M; Charlson, Emily S; Pearson, Denise J; Chung, Daniel C; Traband, Anastasia; Pan, Wei; Ying, Gui-Shuang; Bennett, Jean; Maguire, Albert M; Morgan, Jessica I W

2017-03-01

To describe in detail the central retinal structure of a large group of patients with choroideremia (CHM). A prospective, cross-sectional, descriptive study. Patients (n = 97, age 6-71 years) with CHM and subjects with normal vision (n = 44; ages 10-50 years) were included. Subjects were examined with spectral-domain optical coherence tomography (SD OCT) and near-infrared reflectance imaging. Visual acuity (VA) was measured during their encounter or obtained from recent ophthalmic examinations. Visual thresholds were measured in a subset of patients (n = 24) with automated static perimetry within the central regions (±15°) examined with SD OCT. Visual acuity and visual thresholds; total nuclear layer, inner nuclear layer (INL), and outer nuclear layer (ONL) thicknesses; and horizontal extent of the ONL and the photoreceptor outer segment (POS) interdigitation zone (IZ). Earliest abnormalities in regions with normally appearing retinal pigment epithelium (RPE) were the loss of the POS and ellipsoid zone associated with rod dysfunction. Transition zones (TZs) from relatively preserved retina to severe ONL thinning and inner retinal thickening moved centripetally with age. Most patients (88%) retained VAs better than 20/40 until their fifth decade of life. The VA decline coincided with migration of the TZ near the foveal center. There were outer retinal tubulations in degenerated, nonatrophic retina in the majority (69%) of patients. In general, RPE abnormalities paralleled photoreceptor degeneration, although there were regions with detectable but abnormally thin ONL co-localizing with severe RPE depigmentation and choroidal thinning. Abnormalities of the POS and rod dysfunction are the earliest central abnormalities observed in CHM. Foveal function is relatively preserved until the fifth decade of life. Migration of the TZs to the foveal center with foveal thinning and structural disorganization heralded central VA loss. The relationships established may help outline the eligibility criteria and outcome measures for clinical trials for CHM. Copyright © 2016 American Academy of Ophthalmology. Published by Elsevier Inc. All rights reserved.

Cooled turbine vane with endcaps

DOEpatents

Cunha, Frank J.; Schiavo, Jr., Anthony L.; Nordlund, Raymond Scott; Malow, Thomas; McKinley, Barry L.

2002-01-01

A turbine vane assembly which includes an outer endcap having a plurality of generally straight passages and passage segments therethrough, an inner endcap having a plurality of passages and passage segments therethrough, and a vane assembly having an outer shroud, an airfoil body, and an inner shroud. The outer shroud, airfoil body and inner shroud each have a plurality of generally straight passages and passage segments therethrough as well. The outer endcap is coupled to the outer shroud so that outer endcap passages and said outer shroud passages form a fluid circuit. The inner endcap is coupled to the inner shroud so that the inner end cap passages and the inner shroud passages from a fluid circuit. Passages in the vane casting are in fluid communication with both the outer shroud passages and the inner shroud passages. Passages in the outer endcap may be coupled to a cooling system that supplies a coolant and takes away the heated exhaust.

STRUCTURAL ASSESSMENT OF HYPERAUTOFLUORESCENT RING IN PATIENTS WITH RETINITIS PIGMENTOSA

PubMed Central

LIMA, LUIZ H.; CELLA, WENER; GREENSTEIN, VIVIENNE C.; WANG, NAN-KAI; BUSUIOC, MIHAI; THEODORE SMITH, R.; YANNUZZI, LAWRENCE A.; TSANG, STEPHEN H.

2009-01-01

Purpose To analyze the retinal structure underlying the hyperautofluorescent ring visible on fundus autofluorescence in patients with retinitis pigmentosa. Methods Twenty-four eyes of 13 patients with retinitis pigmentosa, aged 13 years to 67 years, were studied. The integrity of the photoreceptor cilia, also known as the inner/outer segment junction of the photoreceptors, the outer nuclear layer, and retinal pigment epithelium, was evaluated outside, across, and inside the ring with spectral-domain optical coherence tomography (OCT). Results Inside the foveal area, fundus autofluorescence did not detect abnormalities. Outside the ring, fundus autofluorescence revealed hypoautofluorescence compatible with the photoreceptor/retinal pigment epithelium degeneration. Spectral-domain OCT inside the ring, in the area of normal foveal fundus autofluorescence, revealed an intact retinal structure in all eyes and total retinal thickness values that were within normal limits. Across the ring, inner/outer segment junction disruption was observed and the outer nuclear layer was decreased in thickness in a centrifugal direction in all eyes. Outside the hyperautofluorescent ring, the inner/outer segment junction and the outer nuclear layer appeared to be absent and there were signs of retinal pigment epithelium degeneration. Conclusion Disruption of the inner/outer segment junction and a decrease in outer retinal thickness were found across the central hyperautofluorescent ring seen in retinitis pigmentosa. Outer segment phagocytosis by retinal pigment epithelium is necessary for the formation of an hyperautofluorescent ring. PMID:19584660

Correlation between spectral-domain OCT findings and visual acuity in X-linked retinoschisis.

PubMed

Yang, Hyun Seung; Lee, Jung Bok; Yoon, Young Hee; Lee, Joo Yong

2014-05-08

To investigate the tomographic characteristics of the outer retina and choroid and their relationship with visual acuity in X-linked juvenile retinoschisis (XLRS) patients using spectral-domain optical coherence tomography (SD-OCT). In this retrospective, observational, case-control study, we analyzed 20 eyes of 10 patients with XLRS using SD-OCT. The clinical and tomographic features of the outer retina, including the external limiting membrane (ELM), inner segment/outer segment (IS/OS) junction, cone cell outer segment tips (COST) line, photoreceptor outer segment (PROS) length, and choroid, were evaluated. As controls, 40 age-, sex-, and refraction-matched healthy eyes (1:2 matched) were randomly selected and imaged in parallel. The most prevalent area of abnormality in the outer retina layer of our patients was the outer plexiform layer (OPL; 60% of all affected eyes) and COST line (75% of all affected eyes). On average, the subfoveal choroid and PROS lengths were 35 μm thicker and 19 μm thinner, respectively, in XLRS patients (P = 0.084 and P < 0.001, respectively). A dominant IS/OS junction, COST line defects, and PROS length were related to patient best-corrected visual acuity (BCVA; P = 0.029, P = 0.001, and P < 0.001, respectively) by univariate analysis. Cone cell outer segment tips line defect and PROS length were the only factors related to BCVA in multivariate analysis (P = 0.028 and 0.003, respectively). Outer plexiform layer and photoreceptor microstructure defects are frequent in XLRS patients. Cone cell outer segment tips line defects and shortened PROS lengths as well as other photoreceptor microstructure defects may be closely related to poor vision in XLRS.

Optical measurements of Na-Ca-K exchange currents in intact outer segments isolated from bovine retinal rods

PubMed Central

1991-01-01

The properties of Na-Ca-K exchange current through the plasma membrane of intact rod outer segments (ROS) isolated from bovine retinas were studied with the optical probe neutral red. Small cellular organelles such as bovine ROS do not offer an adequate collecting area to measure Na-Ca-K exchange currents with electrophysiological techniques. This study demonstrates that Na-Ca-K exchange current in bovine ROS can be measured with the dye neutral red and dual-wavelength spectrophotometry. The binding of neutral red is sensitive to transport of cations across the plasma membrane of ROS by the effect of the translocated cations on the surface potential of the intracellular disk membranes (1985. J. Membr. Biol. 88: 249-262). Electrogenic Na+ fluxes through the ROS plasma membrane were measured with a resolution of 10(5) Na+ ions/ROS per s, equivalent to a current of approximately 0.01 pA; maximal electrogenic Na-Ca-K exchange flux in bovine ROS was equivalent to a maximal exchange current of 1-2 pA. Electrogenic Na+ fluxes were identified as Na-Ca-K exchange current based on a comparison between electrogenic Na+ flux and Na(+)-stimulated Ca2+ release with respect to flux rate, Na+ dependence, and ion selectivity. Neutral red monitored the net entry of a single positive charge carried by Na+ for each Ca2+ ion released (i.e., monitored the Na-Ca-K exchange current). Na-Ca-K exchange in the plasma membrane of bovine ROS had the following properties: (a) Inward Na-Ca-K exchange current required internal Ca2+ (half-maximal stimulation at a free Ca2+ concentration of 0.9 microM), whereas outward Na-Ca-K exchange current required both external Ca2+ (half-maximal stimulation at a free Ca2+ concentration of 1.1 microM) and external K+. (b) Inward Na-Ca-K exchange current depended in a sigmoidal manner on the external Na+ concentration, identical to Na(+)-stimulated Ca2+ release measured with Ca(2+)- indicating dyes. (c) The neutral red method was modified to measure Ca(2+)-activated K+ fluxes (half-maximal stimulation at 2.7 microM free Ca2+) via the Na-Ca-K exchanger in support of the notion that the rod Na-Ca exchanger is in effect a Na-Ca-K exchanger. (d) Competitive interactions between Ca2+ and Na+ ions on the exchanger protein are described. PMID:1722239

C2orf71a/pcare1 is important for photoreceptor outer segment morphogenesis and visual function in zebrafish.

PubMed

Corral-Serrano, Julio C; Messchaert, Muriël; Dona, Margo; Peters, Theo A; Kamminga, Leonie M; van Wijk, Erwin; Collin, Rob W J

2018-06-26

Mutations in C2orf71 are causative for autosomal recessive retinitis pigmentosa and occasionally cone-rod dystrophy. We have recently discovered that the protein encoded by this gene is important for modulation of the ciliary membrane through the recruitment of an actin assembly module, and have therefore renamed the gene to PCARE (photoreceptor cilium actin regulator). Here, we report on the identification of two copies of the c2orf71/pcare gene in zebrafish, pcare1 and pcare2. To study the role of the gene most similar to human PCARE, pcare1, we have generated a stable pcare1 mutant zebrafish model (designated pcare1 rmc100/rmc100 ) in which the coding sequence was disrupted using CRISPR/Cas9 technology. Retinas of both embryonic (5 dpf) and adult (6 mpf) pcare1 rmc100/rmc100 zebrafish display a clear disorganization of photoreceptor outer segments, resembling the phenotype observed in Pcare -/- mice. Optokinetic response and visual motor response measurements indicated visual impairment in pcare1 rmc100/rmc100 zebrafish larvae at 5 dpf. In addition, electroretinogram measurements showed decreased b-wave amplitudes in pcare1 rmc100/rmc100 zebrafish as compared to age- and strain-matched wild-type larvae, indicating a defect in the transretinal current. Altogether, our data show that lack of pcare1 causes a retinal phenotype in zebrafish and indicate that the function of the PCARE gene is conserved across species.

Coaxial stub tuner

NASA Technical Reports Server (NTRS)

Chern, Shy-Shiun (Inventor)

1981-01-01

A coaxial stub tuner assembly is comprised of a short circuit branch diametrically opposite an open circuit branch. The stub of the short circuit branch is tubular, and the stub of the open circuit branch is a rod which extends through the tubular stub into the open circuit branch. The rod is threaded at least at its outer end, and the tubular stub is internally threaded to receive the threads of the rod. The open circuit branch can be easily tuned by turning the threaded rod in the tubular stub to adjust the length of the rod extending into the open circuit branch.

Electrically operated magnetic switch designed to display reduced leakage inductance

DOEpatents

Cook, Edward G.

1994-01-01

An electrically operated magnetic switch is disclosed herein for use in opening and closing a circuit between two terminals depending upon the voltage across these terminals. The switch so disclosed is comprised of a ferrite core in the shape of a toroid having opposing ends and opposite inner and outer sides and an arrangement of electrically conductive components defining at least one current flow path which makes a number of turns around the core. This arrangement of components includes a first plurality of electrically conducive rigid rods parallel with and located outside the outer side of the core and a second plurality of electrically conductive rigid rods parallel with and located inside the inner side of the core. The arrangement also includes means for electrically connecting these rods together so that the define the current flow path. In one embodiment, this latter means uses rigid cross-tab means. In another, preferred embodiment, printed circuits on rigid dielectric substrates located on opposite ends of the core are utilized to interconnect the rods together.

Experimental chloroquine retinopathy.

PubMed

Matsumura, M; Ohkuma, M; Tsukahara, I

1986-01-01

Chloroquine retinopathy was produced experimentally in the eye of the albino corydoras (one of the tropical fish) by daily administration of chloroquine (0.1 mg per os). The enucleated eyes were examined from the 14th day to 3 months after the beginning of drug administration under light and electron microscopy. The first change of retina was the appearance of membraneous cytoplasmic body (MCB) in the cytoplasm of ganglion, amacrine, bipolar and horizontal cells. MCB might be degenerated lysosome. They showed lamellar figures or crystalline lattice-like structures. Secondarily, these MCB appeared in the inner segments of photoreceptor cells. The outer segments of rod cells disappeared, and then those of cone cells. Although photoreceptor cells were diminished in number in advanced degeneration, the cells of inner nuclear layer and ganglion cells were maintained in number. The presence of MCB dose not mean death of cells. The retinal pigment epithelial cells contained MCB in its cytoplasm only in severe degenerative cases, and did not show other remarkable changes. MCB also appeared in the cytoplasm of pericytes of retinal vessels. Chloroquine is considered to damage directly photoreceptor cells most severely.

ADP-ribosylation of transducin by pertussis toxin

DOE Office of Scientific and Technical Information (OSTI.GOV)

Watkins, P.A.; Burns, D.L.; Kanaho, Y.

1985-11-05

Transducin, the guanyl nucleotide-binding regulatory protein of retinal rod outer segments that couples the photon receptor, rhodopsin, with the light-activated cGMP phosphodiesterase, can be resolved into two functional components, T alpha and T beta gamma. T alpha (39 kDa), which is (TSP)ADP-ribosylated by pertussis toxin and (TSP)NAD in rod outer segments and in purified transducin, was also labeled by the toxin after separation from T beta gamma (36 kDa and approximately 10 kDa); neither component of T beta gamma was a pertussis toxin substrate. Labeling of T alpha was enhanced by T beta gamma and was maximal at approximately 1:1more » molar ratio of T alpha : T beta gamma. Limited proteolysis by trypsin of T alpha in the presence of guanyl-5'-yl imidodiphosphate (Gpp(NH)p) resulted in the sequential appearance of proteins of 38 and TS kDa. The amino terminus of both 38- and TS-kDa proteins was leucine, whereas that of T alpha could not be identified and was assumed to be blocked. The TS-kDa peptide was not a pertussis toxin substrate. Labeling of the 38-kDa protein was poor and was not enhanced by T beta gamma. Trypsin treatment of (TSP)ADP-ribosyl-T alpha produced a labeled 37-38-kDa doublet followed by appearance of radioactivity at the dye front. It appears, therefore, that, although the 38-kDa protein was poor toxin substrate, it contained the ADP-ribosylation site. Without rhodopsin, labeling of T alpha (in the presence of T beta gamma) was unaffected by Gpp(NH)p, guanosine 5'-O-(thiotriphosphate) (GTP gamma S), GTP, GDP, and guanosine 5'-O-(thiodiphosphate) (GDP beta S) but was increased by ATP. When photolyzed rhodopsin and T beta gamma were present, Gpp(NH)p and GTP gamma S decreased (TSP)ADP-ribosylation by pertussis toxin. Thus, pertussis toxin-catalyzed (TSP)ADP-ribosylation of T alpha was affected by nucleotides, rhodopsin and light in addition to T beta gamma.« less

Evolution of Vision

NASA Astrophysics Data System (ADS)

Ostrovsky, Mikhail

The evolution of photoreception, giving rise to eye, offers a kaleidoscopic view on selection acting at both the organ and molecular levels. The molecular level is mainly considered in the lecture. The greatest progress to date has been made in relation to the opsin visual pigments. Opsins appeared before eyes did. Two- and three-dimensional organization for rhodopsin in the rod outer segment disk membrane, as well as molecular mechanisms of visual pigments spectral tuning, photoisomerization and also opsin as a G-protein coupled receptor are considered. Molecular mechanisms of visual pigments spectral tuning, namely switching of chromophore (physiological time scale) and amino acid changes in the chromophore site of opsin (evolutionary time scale) is considered in the lecture. Photoisomerization of rhodopsin chromophore, 11-cis retinal is the only photochemical reaction in vision. The reaction is extemely fast (less that 200 fs) and high efficient (. is 0.65). The rhodopsin photolysis and kinetics of the earlier products appearance, photo- and bathorhodopsin, is considered. It is known that light is not only a carrier of information, but also a risk factor of damage to the eye. This photobiological paradox of vision is mainly due to the nature of rhodopsin chromophore. Photooxidation is the base of the paradox. All factors present in the phototrceptor cells to initiate free-radical photooxidation: photosensitizers, oxygen and substrates of oxidation: lipids and proteins (opsin). That is why photoprotective system of the eye structures appeared in the course of evolution. Three lines of protective system to prevent light damage to the retina and retina pigment epithelium is known: permanent renewal of rod and cone outer segment, powerful antioxidant system and optical media as cut-off filters where the lens is a key component. The molecular mechanisms of light damage to the eye and photoprotective system of the eye is considered in the lecture. The molecular mechanisms of phototransduction in vertebrates eye is also briefly considered in the lecture. Evolution of vision is an enormous subject for thought and investigation. In the postgenomic era evolutionary molecular physiology as a whole and evolutionary molecular physiology of vision can be considered as a key approach for understanding how genome is working.

Rod outer segment-associated N-acetylgalactosaminylphosphotransferase.

PubMed

Sweatt, A J; Balsamo, J; Lilien, J

1995-01-01

To determine the exact location of a cell surface glycosyltransferase (N-acetylgalactosaminylphosphotransferase, (GalNAcPTase) immunochemically identified in mammalian rod outer segments (ROS), to determine whether anti-GalNAcPTase antibody recognizes retinal molecules that possess transferase activity and to characterize ROS transferase enzyme activity and acceptors. The GalNAcPTase is known to be associated with the adhesion molecule N-cadherin in embryonic avian retinas and with E-cadherin in mammalian pancreatic islet cells. Purified, fixed ROS were reacted with anti-chick GalNAcPTase antibody followed by secondary antibody conjugated to colloidal gold and were examined by electron microscopy. Fractions of retinal and ROS proteins enriched in the transferase were obtained through batch adsorption on Sepharose, separated by gel electrophoresis, transferred to nitrocellulose, and either reacted with anti-GalNAcPTase antibody or assayed for transferase activity. Interphotoreceptor matrix (IPM) was examined for the presence of immunoreactive GalNAcPTase by gel electrophoresis and immunoblot. The kinetics and endogenous acceptors of the cow ROS transferase were characterized. ROS are specifically labeled by anti-GalNAcPTase antibody at the cell surface. The immunogold label was associated with the cell surface and with flocculent material adherent to the cell surface. In addition, soluble and particulate fractions of the IPM showed GalNAcPTase-like immunoreactivity. The transferase appears as single immunoreactive band at or near 220 kd. Transferase enzyme activity was present at this position on Western transfers of retinal and ROS proteins. In whole ROS, transferase activity was directed toward endogenous acceptors of very high molecular mass. The GalNAcPTase is localized on ROS in association with the cell surface and with components of the IPM. The molecule recognized by the anti-GalNAcPTase antibody possesses transferase activity toward itself and a few other proteins, but mostly toward very large molecules that may be IPM proteoglycans. It is not yet known whether the enzyme of the adult retina specifically transfers sugar or sugar-phosphate groups to its acceptors. It is proposed that the ROS GalNAcPTase is involved in the modulation of adhesive phenomena between or within photoreceptors or between photoreceptors and the interphotoreceptor matrix.

Energetics of primary processes in visula escitation: photocalorimetry of rhodopsin in rod outer segment membranes.

PubMed

Cooper, A; Converse, C A

1976-07-13

A sensitive technique for the direct calorimetric determination of the energetics of photochemical reactions under low levels of illumination, and its application to the study of primary processes in visula excitation, are described. Enthlpies are reported for various steps in the bleaching of rhodopsin in intact rod outer segment membranes, together with the heats of appropriate model reactions. Protonation changes are also determined calorimetrically by use of buffers with differing heats of proton ionization. Bleaching of rhodopsin is accompanied by significant uptake of heat energy, vastly in excess of the energy required for simple isomerization of the retinal chromophore. Metarhodopsin I formation involves the uptake of about 17 kcal/mol and no net change in proton ionization of the system. Formation of metarhodopsin II requires an additional energy of about 10 kcal/mol and involves the uptake on one hydrogen ion from solution. The energetics of the overall photolysis reaction, rhodopsin leads to opsin + all-trans-retinal, are pH dependent and involve the exposure of an additional titrating group on opsin. This group has a heat of proton ionization of about 12 kcal/mal, characteristic of a primary amine, but a pKa in the region of neutrality. We suggest that this group is the Schiff base lysine of the chromophore binding site of rhodopsin which becomes exposed on photolysis. The low pKa for this active lysine would result in a more stable retinal-opsin linkage, and might be induced by a nearby positively charged group on the protein (either arginine or a second lysine residue). This leads to a model involving intramolecular protonation of the Schiff base nitrogen in the retinal-opsin linkage of rhodopsin, which is consistent with the thermodynamic and spectroscopic properties of the system. We further propose that the metarhodopsin I leads to metarhodopsin II step in the bleaching sequence involves reversible hydrolysis of the Schiff base linkage in the chromophore binding site, and that subsequent steps are the result of migration of the chromophore from this site.

Photocurrents in retinal rods of pigeons (Columba livia): kinetics and spectral sensitivity.

PubMed Central

Palacios, A G; Goldsmith, T H

1993-01-01

1. Membrane photocurrents were recorded from outer segments of isolated retinal rods of pigeons (Columba livia), the first such measurements on the photoreceptors of a bird. The amplitude of the response to 20 ms flashes of narrow wavelength bands of light increases linearly with intensity at low photon fluxes and saturates at higher intensities. The maximum (saturating) photocurrent observed in forty-nine rod cells was 50 pA. Larger responses with less variability in the intensity for half-maximal responses were observed when the physiological saline contained 20 mM bicarbonate (in addition to Hepes buffer). 2. The dependence of peak amplitude on intensity is well fitted by an exponential function; it is usually less well fitted by the Michaelis-Menten (Naka-Rushton) equation. 3. In the presence of bicarbonate, the average sensitivity of pigeon rods to dim flashes was 0.56 pA photon-1 microns -2. The effective collecting area per photon was 1.8 microns 2. About 83 +/- 26 (mean +/- S.D.) photoisomerizations were required for a half-saturating response. 4. The response kinetics of rods to dim flashes can be reasonably well described by a series of four to five either Poisson or independent filters. The time to peak, measured from the mid-point of a 20 ms flash, was 319 +/- 83 ms (mean +/- S.D.). The integration time of the response was 851 +/- 86 ms (mean +/- S.D.) with bicarbonate present and 572 +/- 126 ms in the absence of bicarbonate. The responses of pigeon rods appear to be slower than those of mammals at the same temperature. The fraction of current suppressed by a single photoisomerization is smaller in pigeon than in mammalian rods by a factor of at least two. 5. The spectral sensitivity function was measured between 680 and 330 nm. The maximum at about 505 nm (range 497-508 nm) corresponds to the alpha-band of a vertebrate rhodopsin and agrees with previous behavioural measurements of scotopic sensitivity of pigeons as well as the absorption spectrum of extracts of pigeon rhodopsin. There was no pronounced beta-band in the near-ultraviolet wavelengths. PMID:8120835

Hidden contributions of the enamel rods on the fracture resistance of human teeth.

PubMed

Yahyazadehfar, M; Bajaj, Devendra; Arola, Dwayne D

2013-01-01

The enamel of human teeth is generally regarded as a brittle material with low fracture toughness. Consequently, the contributions of this tissue in resisting tooth fracture and the importance of its complex microstructure have been largely overlooked. In this study an experimental evaluation of the crack growth resistance of human enamel was conducted to characterize the role of rod (i.e. prism) orientation and degree of decussation on the fracture behavior of this tissue. Incremental crack growth was achieved in-plane, with the rods in directions longitudinal or transverse to their axes. Results showed that the fracture resistance of enamel is both inhomogeneous and spatially anisotropic. Cracks extending transverse to the rods in the outer enamel undergo a lower rise in toughness with extension, and achieve significantly lower fracture resistance than in the longitudinal direction. Though cracks initiating at the surface of teeth may begin extension towards the dentin-enamel junction, they are deflected by the decussated rods and continue growth about the tooth's periphery, transverse to the rods in the outer enamel. This process facilitates dissipation of fracture energy and averts cracks from extending towards the dentin and vital pulp. Copyright © 2012 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Eulerian Formulation of Spatially Constrained Elastic Rods

NASA Astrophysics Data System (ADS)

Huynen, Alexandre

Slender elastic rods are ubiquitous in nature and technology. For a vast majority of applications, the rod deflection is restricted by an external constraint and a significant part of the elastic body is in contact with a stiff constraining surface. The research work presented in this doctoral dissertation formulates a computational model for the solution of elastic rods constrained inside or around frictionless tube-like surfaces. The segmentation strategy adopted to cope with this complex class of problems consists in sequencing the global problem into, comparatively simpler, elementary problems either in continuous contact with the constraint or contact-free between their extremities. Within the conventional Lagrangian formulation of elastic rods, this approach is however associated with two major drawbacks. First, the boundary conditions specifying the locations of the rod centerline at both extremities of each elementary problem lead to the establishment of isoperimetric constraints, i.e., integral constraints on the unknown length of the rod. Second, the assessment of the unilateral contact condition requires, in principle, the comparison of two curves parametrized by distinct curvilinear coordinates, viz. the rod centerline and the constraint axis. Both conspire to burden the computations associated with the method. To streamline the solution along the elementary problems and rationalize the assessment of the unilateral contact condition, the rod governing equations are reformulated within the Eulerian framework of the constraint. The methodical exploration of both types of elementary problems leads to specific formulations of the rod governing equations that stress the profound connection between the mechanics of the rod and the geometry of the constraint surface. The proposed Eulerian reformulation, which restates the rod local equilibrium in terms of the curvilinear coordinate associated with the constraint axis, describes the rod deformed configuration by means of either its relative position with respect to the constraint axis (contact-free segments) or its angular position on the constraint surface (continuous contacts.) This formulation circumvents both drawbacks that afflict the conventional Lagrangian approach associated with the segmentation strategy. As the a priori unknown domain, viz. the rod length, is substituted for the known constraint axis, the free boundary problem and the associated isoperimetric constraints are converted into a classical two-point boundary value problem. Additionally, the description of the rod deflection by means of its eccentricity with respect to the constraint axis trivializes the assessment of the unilateral contact condition. Along continuous contacts, this formulation expresses the strain variables, measuring the rod change of shape, in terms of the geometric invariants of the constraint surface, and emphasizes the influence of the constraint local geometry on the reaction pressure. Formalizing the segmentation strategy, a computational model that exploits the Eulerian formulation of the rod governing equations is devised. To solve the quasi-static deflection of elastic rods constrained inside or around a tube-like surface, this computational model identifies the number of contacts, their nature (either discrete or continuous), and the rod configuration at the connections that satisfies the unilateral contact condition and preserves the rod integrity along the sequence of elementary problems.

Method of fabricating a prestressed cast iron vessel

DOEpatents

Lampe, Robert F.

1982-01-01

A method of fabricating a prestressed cast iron vessel wherein double wall cast iron body segments each have an arcuate inner wall and a spaced apart substantially parallel outer wall with a plurality of radially extending webs interconnecting the inner wall and the outer wall, the bottom surface and the two exposed radial side surfaces of each body segment are machined and eight body segments are formed into a ring. The top surfaces and outer surfaces of the outer walls are machined and keyways are provided across the juncture of adjacent end walls of the body segments. A liner segment complementary in shape to a selected inner wall of one of the body segments is mounted to each of the body segments and again formed into a ring. The liner segments of each ring are welded to form unitary liner rings and thereafter the cast iron body segments are prestressed to complete the ring assembly. Ring assemblies are stacked to form the vessel and adjacent unitary liner rings are welded. A top head covers the top ring assembly to close the vessel and axially extending tendons retain the top and bottom heads in place under pressure.

Depletion of calcium stores regulates calcium influx and signal transmission in rod photoreceptors

PubMed Central

Szikra, Tamas; Cusato, Karen; Thoreson, Wallace B; Barabas, Peter; Bartoletti, Theodore M; Krizaj, David

2008-01-01

Tonic synapses are specialized for sustained calcium entry and transmitter release, allowing them to operate in a graded fashion over a wide dynamic range. We identified a novel plasma membrane calcium entry mechanism that extends the range of rod photoreceptor signalling into light-adapted conditions. The mechanism, which shares molecular and physiological characteristics with store-operated calcium entry (SOCE), is required to maintain baseline [Ca2+]i in rod inner segments and synaptic terminals. Sustained Ca2+ entry into rod cytosol is augmented by store depletion, blocked by La3+ and Gd3+ and suppressed by organic antagonists MRS-1845 and SKF-96365. Store depletion and the subsequent Ca2+ influx directly stimulated exocytosis in terminals of light-adapted rods loaded with the activity-dependent dye FM1–43. Moreover, SOCE blockers suppressed rod-mediated synaptic inputs to horizontal cells without affecting presynaptic voltage-operated Ca2+ entry. Silencing of TRPC1 expression with small interference RNA disrupted SOCE in rods, but had no effect on cone Ca2+ signalling. Rods were immunopositive for TRPC1 whereas cone inner segments immunostained with TRPC6 channel antibodies. Thus, SOCE modulates Ca2+ homeostasis and light-evoked neurotransmission at the rod photoreceptor synapse mediated by TRPC1. PMID:18755743

Development and Assessment of a New CFRP Rod Anchor System for Prestressed Concrete

NASA Astrophysics Data System (ADS)

Al-Mayah, A.; Soudki, K.; Plumtree, A.

2006-09-01

Design concepts and experimental assessment of a new wedge anchor system for prestressing CFRP rods are presented. This compact and reusable anchor consists of an outer cylinder (barrel), a number of wedges, and a soft metal sleeve. The contacting surfaces of the wedges and barrel have a circular profile along the length of the anchor. Tensile testing using different presetting loads, geometric configurations, and rod sizes was carried out. The relationship of the tensile load and displacement of the rod was established. Presetting was found unnecessary since the anchor system was found to be capable of carrying the full design strength of the rods.

Calcium Sensing by Recoverin: Effect of Protein Conformation on Ion Affinity.

PubMed

Timr, Štěpán; Kadlec, Jan; Srb, Pavel; Ollila, O H Samuli; Jungwirth, Pavel

2018-04-05

The detailed functional mechanism of recoverin, which acts as a myristoyl switch at the rod outer-segment disk membrane, is elucidated by direct and replica-exchange molecular dynamics. In accord with NMR structural evidence and calcium binding assays, simulations point to the key role of enhanced calcium binding to the EF3 loop of the semiopen state of recoverin as compared to the closed state. This 2-4-order decrease in calcium dissociation constant stabilizes the semiopen state in response to the increase of cytosolic calcium concentration in the vicinity of recoverin. A second calcium ion then binds to the EF2 loop and, consequently, the structure of the protein changes from the semiopen to the open state. The latter has the myristoyl chain extruded to the cytosol, ready to act as a membrane anchor of recoverin.

Modulating DNA configuration by interfacial traction: an elastic rod model to characterize DNA folding and unfolding.

PubMed

Huang, Zaixing

2011-01-01

As a continuum model of DNA, a thin elastic rod subjected to interfacial interactions is used to investigate the equilibrium configuration of DNA in intracellular solution. The interfacial traction between the rod and the solution environment is derived in detail. Kirchhoff's theory of elastic rods is used to analyze the equilibrium configuration of a DNA segment under the action of the interfacial traction. The influences of the interfacial energy factor and bending stiffness on the toroidal spool formation of the DNA segment are discussed. The results show that the equilibrium configuration of DNA is mainly determined by competition between the interfacial energy and elastic strain energy of the DNA itself, and the interfacial traction is one of the forces that drives DNA folding and unfolding.

Nuclear reactor control apparatus

DOEpatents

Sridhar, Bettadapur N.

1983-10-25

Nuclear reactor safety rod release apparatus comprises a ring which carries detents normally positioned in an annular recess in outer side of the rod, the ring being held against the lower end of a drive shaft by magnetic force exerted by a solenoid carried by the drive shaft. When the solenoid is de-energized, the detent-carrying ring drops until the detents contact a cam surface associated with the lower end of the drive shaft, at which point the detents are cammed out of the recess in the safety rod to release the rod from the drive shaft. In preferred embodiments of the invention, an additional latch is provided to release a lower portion of a safety rod under conditions that may interfere with movement of the entire rod.

Leaf seal for inner and outer casings of a turbine

DOEpatents

Schroder, Mark Stewart; Leach, David

2002-01-01

A plurality of arcuate, circumferentially extending leaf seal segments form an annular seal spanning between annular sealing surfaces of inner and outer casings of a turbine. The ends of the adjoining seal segments have circumferential gaps to enable circumferential expansion and contraction of the segments. The end of a first segment includes a tab projecting into a recess of a second end of a second segment. Edges of the tab seal against the sealing surfaces of the inner and outer casings have a narrow clearance with opposed edges of the recess. An overlying cover plate spans the joint. Leakage flow is maintained at a minimum because of the reduced gap between the radially spaced edges of the tab and recess, while the seal segments retain the capacity to expand and contract circumferentially.

Nuclear reactor safety device

DOEpatents

Hutter, Ernest

1986-01-01

A safety device is disclosed for use in a nuclear reactor for axially repositioning a control rod with respect to the reactor core in the event of an upward thermal excursion. Such safety device comprises a laminated helical ribbon configured as a tube-like helical coil having contiguous helical turns with slidably abutting edges. The helical coil is disclosed as a portion of a drive member connected axially to the control rod. The laminated ribbon is formed of outer and inner laminae. The material of the outer lamina has a greater thermal coefficient of expansion than the material of the inner lamina. In the event of an upward thermal excursion, the laminated helical coil curls inwardly to a smaller diameter. Such inward curling causes the total length of the helical coil to increase by a substantial increment, so that the control rod is axially repositioned by a corresponding amount to reduce the power output of the reactor.

Electrically operated magnetic switch designed to display reduced leakage inductance

DOEpatents

Cook, E.G.

1994-05-10

An electrically operated magnetic switch is disclosed herein for use in opening and closing a circuit between two terminals depending upon the voltage across these terminals. The switch so disclosed is comprised of a ferrite core in the shape of a toroid having opposing ends and opposite inner and outer sides and an arrangement of electrically conductive components defining at least one current flow path which makes a number of turns around the core. This arrangement of components includes a first plurality of electrically conducive rigid rods parallel with and located outside the outer side of the core and a second plurality of electrically conductive rigid rods parallel with and located inside the inner side of the core. The arrangement also includes means for electrically connecting these rods together so that the define the current flow path. In one embodiment, this latter means uses rigid cross-tab means. In another, preferred embodiment, printed circuits on rigid dielectric substrates located on opposite ends of the core are utilized to interconnect the rods together. 10 figures.

Resistively heated shape memory polymer device

DOEpatents

Marion, III, John E.; Bearinger, Jane P.; Wilson, Thomas S.; Maitland, Duncan J.

2017-09-05

A resistively heated shape memory polymer device is made by providing a rod, sheet or substrate that includes a resistive medium. The rod, sheet or substrate is coated with a first shape memory polymer providing a coated intermediate unit. The coated intermediate unit is in turn coated with a conductive material providing a second intermediate unit. The second coated intermediate unit is in turn coated with an outer shape memory polymer. The rod, sheet or substrate is exposed and an electrical lead is attached to the rod, sheet or substrate. The conductive material is exposed and an electrical lead is attached to the conductive material.

Resistively heated shape memory polymer device

DOEpatents

Marion, III, John E.; Bearinger, Jane P.; Wilson, Thomas S.; Maitland, Duncan J.

2016-10-25

A resistively heated shape memory polymer device is made by providing a rod, sheet or substrate that includes a resistive medium. The rod, sheet or substrate is coated with a first shape memory polymer providing a coated intermediate unit. The coated intermediate unit is in turn coated with a conductive material providing a second intermediate unit. The second coated intermediate unit is in turn coated with an outer shape memory polymer. The rod, sheet or substrate is exposed and an electrical lead is attached to the rod, sheet or substrate. The conductive material is exposed and an electrical lead is attached to the conductive material.

Correction of the retinal dystrophy phenotype of the RCS rat by viral gene transfer of Mertk.

PubMed

Vollrath, D; Feng, W; Duncan, J L; Yasumura, D; D'Cruz, P M; Chappelow, A; Matthes, M T; Kay, M A; LaVail, M M

2001-10-23

The Royal College of Surgeons (RCS) rat is a widely studied animal model of retinal degeneration in which the inability of the retinal pigment epithelium (RPE) to phagocytize shed photoreceptor outer segments leads to a progressive loss of rod and cone photoreceptors. We recently used positional cloning to demonstrate that the gene Mertk likely corresponds to the retinal dystrophy (rdy) locus of the RCS rat. In the present study, we sought to determine whether gene transfer of Mertk to a RCS rat retina would result in correction of the RPE phagocytosis defect and preservation of photoreceptors. We used subretinal injection of a recombinant replication-deficient adenovirus encoding rat Mertk to deliver the gene to the eyes of young RCS rats. Electrophysiological assessment of animals 30 days after injection revealed an increased sensitivity of treated eyes to low-intensity light. Histologic and ultrastructural assessment demonstrated substantial sparing of photoreceptors, preservation of outer segment structure, and correction of the RPE phagocytosis defect in areas surrounding the injection site. Our results provide definitive evidence that mutation of Mertk underlies the RCS retinal dystrophy phenotype, and that the phenotype can be corrected by treatment of juvenile animals. To our knowledge, this is the first demonstration of complementation of both a functional cellular defect (phagocytosis) and a photoreceptor degeneration by gene transfer to the RPE. These results, together with the recent discovery of MERTK mutations in individuals with retinitis pigmentosa, emphasize the importance of the RCS rat as a model for gene therapy of diseases that arise from RPE dysfunction.

Complete volumetric decomposition of individual trabecular plates and rods and its morphological correlations with anisotropic elastic moduli in human trabecular bone.

PubMed

Liu, X Sherry; Sajda, Paul; Saha, Punam K; Wehrli, Felix W; Bevill, Grant; Keaveny, Tony M; Guo, X Edward

2008-02-01

Trabecular plates and rods are important microarchitectural features in determining mechanical properties of trabecular bone. A complete volumetric decomposition of individual trabecular plates and rods was used to assess the orientation and morphology of 71 human trabecular bone samples. The ITS-based morphological analyses better characterize microarchitecture and help predict anisotropic mechanical properties of trabecular bone. Standard morphological analyses of trabecular architecture lack explicit segmentations of individual trabecular plates and rods. In this study, a complete volumetric decomposition technique was developed to segment trabecular bone microstructure into individual plates and rods. Contributions of trabecular type-associated morphological parameters to the anisotropic elastic moduli of trabecular bone were studied. Seventy-one human trabecular bone samples from the femoral neck (FN), tibia, and vertebral body (VB) were imaged using muCT or serial milling. Complete volumetric decomposition was applied to segment trabecular bone microstructure into individual plates and rods. The orientation of each individual trabecula was determined, and the axial bone volume fractions (aBV/TV), axially aligned bone volume fraction along each orthotropic axis, were correlated with the elastic moduli. The microstructural type-associated morphological parameters were derived and compared with standard morphological parameters. Their contributions to the anisotropic elastic moduli, calculated by finite element analysis (FEA), were evaluated and compared. The distribution of trabecular orientation suggested that longitudinal plates and transverse rods dominate at all three anatomic sites. aBV/TV along each axis, in general, showed a better correlation with the axial elastic modulus (r(2) = 0.95 approximately 0.99) compared with BV/TV (r(2) = 0.93 approximately 0.94). The plate-associated morphological parameters generally showed higher correlations with the corresponding standard morphological parameters than the rod-associated parameters. Multiple linear regression models of six elastic moduli with individual trabeculae segmentation (ITS)-based morphological parameters (adjusted r(2) = 0.95 approximately 0.98) performed equally well as those with standard morphological parameters (adjusted r(2) = 0.94 approximately 0.97) but revealed specific contributions from individual trabecular plates or rods. The ITS-based morphological analyses provide a better characterization of the morphology and trabecular orientation of trabecular bone. The axial loading of trabecular bone is mainly sustained by the axially aligned trabecular bone volume. Results suggest that trabecular plates dominate the overall elastic properties of trabecular bone.

Detailed Functional and Structural Phenotype of Bietti Crystalline Dystrophy Associated with Mutations in CYP4V2 Complicated by Choroidal Neovascularization

PubMed Central

Fuerst, Nicole M.; Serrano, Leona; Han, Grace; Morgan, Jessica I. W.; Maguire, Albert M.; Leroy, Bart P.; Kim, Benjamin J.; Aleman, Tomas S.

2016-01-01

Purpose To describe in detail the phenotype of a patient with Bietti crystalline dystrophy (BCD) complicated by choroidal neovascularization (CNV) and the response to intravitreal Bevacizumab (Avastin ®; Genentech/Roche). Methods A 34-year-old woman with BCD and mutations in CYP4V2 (c.802-8_806del13/p.H331P:c992A>C) underwent a complete ophthalmic examination, full-field flash electroretinography (ERG), kinetic and two-color dark-adapted perimetry, and dark-adaptometry. Imaging was performed with spectral domain optical coherence tomography (SD-OCT), near infrared (NIR) and short wavelength (SW) fundus autofluorescence (FAF), and fluorescein angiography (FA). Results Best-corrected visual acuity (BCVA) was 20/20 and 20/60 for the right and left eye, respectively. There were corneal paralimbal crystal-like deposits. Kinetic fields were normal in peripheral extent. Retinal crystals were most obvious on NIR-reflectance and corresponded with hyperreflectivities within the RPE on SD-OCT. There was parafoveal/perifoveal hypofluorescence on SW-FAF and NIR-FAF. Rod > cone sensitivity loss surrounded fixation and extended to ~10° of eccentricity corresponding to regions of photoreceptor outer segment-retinal pigmented epithelium (RPE) interdigitation abnormalities. The outer nuclear layer was normal in thickness. Recovery of sensitivity following a ~76% rhodopsin bleach was normal. ERGs were normal. A subretinal hemorrhage in the left eye co-localized with elevation of the RPE on SD-OCT and leakage on FA, suggestive of CNV. Three monthly intravitreal injections of Bevacizumab led to restoration of BCVA to baseline (20/25). Conclusion Crystals in BCD were predominantly located within the RPE. Photoreceptor outer segment and apical RPE abnormalities underlie the relatively extensive retinal dysfunction observed in relatively early-stage BCD. Intravitreal Bevacizumab was effective in treating CNV in this setting. PMID:27028354

Reactor coolant pump flywheel

DOEpatents

Finegan, John Raymond; Kreke, Francis Joseph; Casamassa, John Joseph

2013-11-26

A flywheel for a pump, and in particular a flywheel having a number of high density segments for use in a nuclear reactor coolant pump. The flywheel includes an inner member and an outer member. A number of high density segments are provided between the inner and outer members. The high density segments may be formed from a tungsten based alloy. A preselected gap is provided between each of the number of high density segments. The gap accommodates thermal expansion of each of the number of segments and resists the hoop stress effect/keystoning of the segments.

Orbital Winch

NASA Technical Reports Server (NTRS)

Hoyt, Robert (Inventor); Slostad, Jeffrey T. (Inventor); Frank, Scott (Inventor); Barnes, Ian M. (Inventor)

2016-01-01

Orbital winch having: lower and upper frames; spool having upper and lower flanges with lower flange attached to lower frame; axial tether guide mounted to upper frame; secondary slewing ring coaxial with spool and rotatably mounted to upper frame, wherein secondary slewing ring's outer surface has gearing; upper tether guide mounted to inner surface of secondary slewing ring; linear translation means having upper end mounted to upper frame and lower end mounted on lower frame; primary slewing ring rotatably mounted within linear translation means allowing translation axially between flanges, wherein primary slewing ring's outer surface has gearing; lower tether guide mounted on primary slewing ring's inner surface; pinion rod having upper end mounted to upper frame and lower end mounted to lower frame, wherein pinion rod's teeth engage primary and secondary slewing rings' outer surface teeth; and tether passing through axial, upper, and lower tether guides and winding around spool.

ARL2BP, a protein linked to Retinitis Pigmentosa, is needed for normal photoreceptor cilia doublets and outer segment structure.

PubMed

Moye, Abigail R; Singh, Ratnesh; Kimler, Victoria A; Dilan, Tanya L; Munezero, Daniella; Saravanan, Thamaraiselvi; Goldberg, Andrew F X; Ramamurthy, Visvanathan

2018-05-02

The outer segment (OS) of photoreceptor cells is an elaboration of a primary cilium with organized stacks of membranous discs that contain the proteins needed for phototransduction and vision. Though cilia formation and function has been well characterized, little is known about the role of cilia in the development of photoreceptor OS. Nevertheless, progress has been made by studying mutations in ciliary proteins which often result in malformed outer segments and lead to blinding diseases. To investigate how ciliary proteins contribute to outer segment formation, we generated a knockout mouse model for ARL2BP, a ciliary protein linked to Retinitis Pigmentosa. The knockout mice display an early and progressive reduction in visual response. Prior to photoreceptor degeneration we observed disorganization of the photoreceptor OS, with vertically aligned discs and shortened axonemes. Interestingly, ciliary doublet microtubule structure was also impaired, displaying open B-tubule doublets, paired with loss of singlet microtubules. Based on results from this study, we conclude that ARL2BP is necessary for photoreceptor cilia doublet formation and axoneme elongation, which is required for outer segment morphogenesis and vision.

SAFETY SYSTEM FOR CONTROL ROD

DOEpatents

Paget, J.A.

1963-05-14

A structure for monitoring the structural continuity of a control rod foi a neutron reactor is presented. A electric conductor readily breakable under mechanical stress is fastened along the length of the control rod at a plurality of positions and forms a closed circuit with remote electrical components responsive to an open circuit. A portion of the conductor between the control rod and said components is helically wound to allow free and normally unrestricted movement of the segment of conductor secured to the control rod relative to the remote components. Any break in the circuit is indicative of control rod breakage. (AEC)

Biomechanical Effects of a Dynamic Topping off Instrumentation in a Long Rigid Pedicle Screw Construct.

PubMed

Reichl, Michael; Kueny, Rebecca A; Danyali, Reza; Obid, Peter; Übeyli, Hüseyin; Püschel, Klaus; Morlock, Michael M; Huber, Gerd; Niemeyer, Thomas; Richter, Alexander

2017-05-01

Biomechanical ex vivo study. To determine if topping off instrumentation can reduce the hypermobility in the adjacent segments when compared with the classic rigid spinal instrumentation. Long rigid instrumentation might increase the mechanical load in the adjacent segments, the resulting hypermobility, and the risk for adjacent segment disease. Topping off instrumentation intends to reduce the hypermobility at the adjacent level by more evenly distributing segmental motion and, thereby, potentially mitigating adjacent level disease. Eight human spines (Th12-L5) were divided into 2 groups. In the rigid group, a 3-segment metal rod instrumentation (L2-L5) was performed. The hybrid group included a 2-segment metal rod instrumentation (L3-L5) with a dynamic topping off instrumentation (L2-L3). Each specimen was tested consecutively in 3 different configurations: native (N=8), 2-segment rod instrumentation (L3-L5, N=8), 3-segment instrumentation (rigid: N=4, hybrid: N=4). For each configuration the range of motion (ROM) of the whole spine and each level was measured by a motion capture system during 5 cycles of extension-flexion (angle controlled to ±5 degrees, 0.1 Hz frequency, no preload). In comparison with the intact spine, both the rigid 3-segment instrumentation and the hybrid instrumentation significantly reduced the ROM in the instrumented segments (L2-L5) while increasing the movement in the adjacent segment L1-L2 (P=0.002, η=0.82) and in Th12-L1 (P<0.001, η=0.90). There were no ROM differences between the rigid and hybrid instrumentation in all segments. Introducing the dynamic topping off did not impart any significant difference in the segmental motion when compared with the rigid instrumentation. Therefore, the current biomechanical study could not show a benefit of using this specific topping off instrumentation to solve the problem of adjacent segment disease.

Long-Term Survival of Photoreceptors Transplanted into the Adult Murine Neural Retina Requires Immune Modulation

PubMed Central

West, Emma L.; Pearson, Rachael A.; Barker, Susie E.; Luhmann, Ulrich F. O.; Maclaren, Robert E.; Barber, Amanda C.; Duran, Yanai; Smith, Alexander J.; Sowden, Jane C.; Ali, Robin R.

2012-01-01

Stem cell therapy presents an opportunity to replace photoreceptors that are lost as a result of inherited and age-related degenerative disease. We have previously shown that murine postmitotic rod photoreceptor precursor cells, identified by expression of the rod-specific transcription factor Nrl, are able to migrate into and integrate within the adult murine neural retina. However, their long-term survival has yet to be determined. Here, we found that integrated Nrl.gfp+ve photoreceptors were present up to 12 months post-transplantation, albeit in significantly reduced numbers. Surviving cells had rod-like morphology, including inner/outer segments and spherule synapses. In a minority of eyes, we observed an early, marked reduction in integrated photoreceptors within 1 month post-transplantation, which correlated with increased numbers of amoeboid macrophages, indicating acute loss of transplanted cells due to an inflammatory response. In the majority of transplants, similar numbers of integrated cells were observed between 1 and 2 months post-transplantation. By 4 months, however, we observed a significant decrease in integrated cell survival. Macrophages and T cells were present around the transplantation site, indicating a chronic immune response. Immune suppression of recipients significantly increased transplanted photoreceptor survival, indicating that the loss observed in unsuppressed recipients resulted from T cell-mediated host immune responses. Thus, if immune responses are modulated, correctly integrated transplanted photoreceptors can survive for extended periods of time in hosts with partially mismatched H-2 haplotypes. These findings suggest that autologous donor cells are optimal for therapeutic approaches to repair the neural retina, though with immune suppression nonautologous donors may be effective. PMID:20857496

Intraoperative pulmonary embolism of Harrington rod during spinal surgery: the potential dangers of rod cutting.

PubMed

Aylott, Caspar E W; Hassan, Kamran; McNally, Donal; Webb, John K

2006-12-01

This is a case report and laboratory-based biomechanics study. The objective is to report the first case of Titanium rod embolisation during scoliosis surgery into the Pulmonary artery. To investigate the potential of an unconstrained cut Titanium rod fragment to cause wounding with reference to recognised weapons. Embolisation of a foreign body to the heart is rare. Bullet embolisation to the heart and lungs is infrequently reported in the last 80 years. Iatrogenic cases of foreign body embolisation are very rare. Fifty 1-2 cm segments of Titanium rod were cut in an unconstrained manner and a novel method was used to calculate velocity. A high-speed camera (6,000 frames/s) was used to further measure velocity and study projectile motion. The wounding potential was investigated using lambs liver, high-speed photography and local dissection. Rod velocities were measured in excess of 23 m s(-1). Rods were seen to tumble end-over-end with a maximum speed of 560 revolutions/s. The maximum kinetic energy was 0.61 J which is approximately 2% that of a crossbow. This is sufficient to cause significant liver damage. The degree of surface damage and internal disruption was influenced by the orientation of the rod fragment at impact. An unconstrained cut segment of a Titanium rod has a significant potential to wound. Precautions should be taken to avoid this potentially disastrous but preventable complication.

Spore formation in Myxococcus xanthus is tied to cytoskeleton functions and polysaccharide spore coat deposition

PubMed Central

Müller, Frank D.; Schink, Christian W.; Hoiczyk, Egbert; Cserti, Emöke; Higgs, Penelope I.

2011-01-01

Summary Myxococcus xanthus is a Gram-negative bacterium that differentiates into environmentally resistant spores. Spore differentiation involves septation-independent remodelling of the rod-shaped vegetative cell into a spherical spore and deposition of a thick and compact spore coat outside of the outer membrane. Our analyses suggest that spore coat polysaccharides are exported to the cell surface by the Exo outer membrane polysaccharide export/polysaccharide co-polymerase 2a (OPX/PCP-2a) machinery. Conversion of the capsule-like polysaccharide layer into a compact spore coat layer requires the Nfs proteins which likely form a complex in the cell envelope. Mutants in either nfs, exo, or two other genetic loci encoding homologs of polysaccharide synthesis enzymes, fail to complete morphogenesis from rods to spherical spores and instead produce a transient state of deformed cell morphology before reversion into typical rods. We additionally provide evidence that the cell cytoskeletal protein, MreB, plays an important role in rod to spore morphogenesis and for spore outgrowth. These studies provide evidence that this novel gram-negative differentiation process is tied to cytoskeleton functions and polysaccharide spore coat deposition. PMID:22188356

NEUTRONIC REACTORS

DOEpatents

Wigner, E.P.; Young, G.J.

1958-10-14

A method is presented for loading and unloading rod type fuel elements of a neutronic reactor of the heterogeneous, solld moderator, liquid cooled type. In the embodiment illustrated, the fuel rods are disposed in vertical coolant channels in the reactor core. The fuel rods are loaded and unloaded through the upper openings of the channels which are immersed in the coolant liquid, such as water. Unloading is accomplished by means of a coffer dam assembly having an outer sleeve which is placed in sealing relation around the upper opening. A radiation shield sleeve is disposed in and reciprocable through the coffer dam sleeve. A fuel rod engaging member operates through the axial bore in the radiation shield sleeve to withdraw the fuel rod from its position in the reactor coolant channel into the shield, the shield snd rod then being removed. Loading is accomplished in the reverse procedure.

S-net : Construction of large scale seafloor observatory network for tsunamis and earthquakes along the Japan Trench

NASA Astrophysics Data System (ADS)

Mochizuki, M.; Uehira, K.; Kanazawa, T.; Shiomi, K.; Kunugi, T.; Aoi, S.; Matsumoto, T.; Sekiguchi, S.; Yamamoto, N.; Takahashi, N.; Nakamura, T.; Shinohara, M.; Yamada, T.

2017-12-01

NIED has launched the project of constructing a seafloor observatory network for tsunamis and earthquakes after the occurrence of the 2011 Tohoku Earthquake to enhance reliability of early warnings of tsunamis and earthquakes. The observatory network was named "S-net". The S-net project has been financially supported by MEXT.The S-net consists of 150 seafloor observatories which are connected in line with submarine optical cables. The total length of submarine optical cable is about 5,500 km. The S-net covers the focal region of the 2011 Tohoku Earthquake and its vicinity regions. Each observatory equips two units of a high sensitive pressure gauges as a tsunami meter and four sets of three-component seismometers. The S-net is composed of six segment networks. Five of six segment networks had been already installed. Installation of the last segment network covering the outer rise area have been finally finished by the end of FY2016. The outer rise segment has special features like no other five segments of the S-net. Those features are deep water and long distance. Most of 25 observatories on the outer rise segment are located at the depth of deeper than 6,000m WD. Especially, three observatories are set on the seafloor of deeper than about 7.000m WD, and then the pressure gauges capable of being used even at 8,000m WD are equipped on those three observatories. Total length of the submarine cables of the outer rise segment is about two times longer than those of the other segments. The longer the cable system is, the higher voltage supply is needed, and thus the observatories on the outer rise segment have high withstanding voltage characteristics. We employ a dispersion management line of a low loss formed by combining a plurality of optical fibers for the outer rise segment cable, in order to achieve long-distance, high-speed and large-capacity data transmission Installation of the outer rise segment was finished and then full-scale operation of S-net has started. All the data from 150 seafloor observatories are being transferred to and stored in the Tsukuba DC. Some data are being transmitted directly to JMA and have been used for monitoring of earthquakes and tsunamis. We will report construction and operation of the S-net system as well as the outline of the obtained data in this presentation.

Colloidosome like structures: self-assembly of silica microrods

DOE PAGES

Datskos, P.; Polizos, G.; Bhandari, M.; ...

2016-03-07

Self-assembly of one-dimensional structures is attracting a great deal of interest because assembled structures can provide better properties compared to individual building blocks. We demonstrate silica microrod self-assembly by exploiting Pickering emulsion based strategy. Micron-sized silica rods were synthesized employing previously reported methods based on polyvinylpyrrolidone/ pentanol emulsion droplets. Moreover, rods self-assembled to make structures in the range of z10 40 mm. Smooth rods assembled better than segmented rods. Finally, the assembled structures were bonded by weak van der Waals forces.

Complete Volumetric Decomposition of Individual Trabecular Plates and Rods and Its Morphological Correlations With Anisotropic Elastic Moduli in Human Trabecular Bone

PubMed Central

Liu, X Sherry; Sajda, Paul; Saha, Punam K; Wehrli, Felix W; Bevill, Grant; Keaveny, Tony M; Guo, X Edward

2008-01-01

Trabecular plates and rods are important microarchitectural features in determining mechanical properties of trabecular bone. A complete volumetric decomposition of individual trabecular plates and rods was used to assess the orientation and morphology of 71 human trabecular bone samples. The ITS-based morphological analyses better characterize microarchitecture and help predict anisotropic mechanical properties of trabecular bone. Introduction Standard morphological analyses of trabecular architecture lack explicit segmentations of individual trabecular plates and rods. In this study, a complete volumetric decomposition technique was developed to segment trabecular bone microstructure into individual plates and rods. Contributions of trabecular type–associated morphological parameters to the anisotropic elastic moduli of trabecular bone were studied. Materials and Methods Seventy-one human trabecular bone samples from the femoral neck (FN), tibia, and vertebral body (VB) were imaged using μCT or serial milling. Complete volumetric decomposition was applied to segment trabecular bone microstructure into individual plates and rods. The orientation of each individual trabecula was determined, and the axial bone volume fractions (aBV/TV), axially aligned bone volume fraction along each orthotropic axis, were correlated with the elastic moduli. The microstructural type–associated morphological parameters were derived and compared with standard morphological parameters. Their contributions to the anisotropic elastic moduli, calculated by finite element analysis (FEA), were evaluated and compared. Results The distribution of trabecular orientation suggested that longitudinal plates and transverse rods dominate at all three anatomic sites. aBV/TV along each axis, in general, showed a better correlation with the axial elastic modulus (r 2 = 0.95∼0.99) compared with BV/TV (r 2 = 0.93∼0.94). The plate-associated morphological parameters generally showed higher correlations with the corresponding standard morphological parameters than the rod-associated parameters. Multiple linear regression models of six elastic moduli with individual trabeculae segmentation (ITS)-based morphological parameters (adjusted r 2 = 0.95∼0.98) performed equally well as those with standard morphological parameters (adjusted r 2 = 0.94∼0.97) but revealed specific contributions from individual trabecular plates or rods. Conclusions The ITS-based morphological analyses provide a better characterization of the morphology and trabecular orientation of trabecular bone. The axial loading of trabecular bone is mainly sustained by the axially aligned trabecular bone volume. Results suggest that trabecular plates dominate the overall elastic properties of trabecular bone. PMID:17907921

Photoreceptor change and visual outcome after idiopathic epiretinal membrane removal with or without additional internal limiting membrane peeling.

PubMed

Ahn, Seong Joon; Ahn, Jeeyun; Woo, Se Joon; Park, Kyu Hyung

2014-01-01

To compare the postoperative photoreceptor status and visual outcome after epiretinal membrane removal with or without additional internal limiting membrane (ILM) peeling. Medical records of 40 eyes from 37 patients undergoing epiretinal membrane removal with residual ILM peeling (additional ILM peeling group) and 69 eyes from 65 patients undergoing epiretinal membrane removal without additional ILM peeling (no additional peeling group) were reviewed. The length of defects in cone outer segment tips, inner segment/outer segment junction, and external limiting membrane line were measured using spectral domain optical coherence tomography images of the fovea before and at 1, 3, 6, and 12 months after the surgery. Cone outer segment tips and inner segment/outer segment junction line defects were most severe at postoperative 1 month and gradually restored at 12 months postoperatively. The cone outer segment tips line defect in the additional ILM peeling group was significantly greater than that in the no additional peeling group at postoperative 1 month (P = 0.006), and best-corrected visual acuity was significantly worse in the former group at the same month (P = 0.001). There was no significant difference in the defect size and best-corrected visual acuity at subsequent visits and recurrence rates between the two groups. Patients who received epiretinal membrane surgery without additional ILM peeling showed better visual and anatomical outcome than those with additional ILM peeling at postoperative 1 month. However, surgical outcomes were comparable between the two groups, thereafter. In terms of visual outcome and photoreceptor integrity, additional ILM peeling may not be an essential procedure.

Turbine nozzle/nozzle support structure

DOEpatents

Boyd, Gary L.; Shaffer, James E.

1997-01-01

An axial flow turbine's nozzle/nozzle support structure having a cantilevered nozzle outer structure including an outer shroud and airfoil vanes extending radially inwardly therefrom, an inner shroud radially adjacent the inner end of the airfoil vanes and cooperatively disposed relative to the outer shroud to provide an annular fluid flow path, an inner and an outer support ring respectively arranged radially inside the inner shroud and axially adjacent a portion of the outer shroud, and pins extending through such portion and into the outer support ring. The inner support ring or inner shroud has a groove therein bounded by end walls for receiving and being axially abuttable with a locating projection from the adjacent airfoil vane, inner shroud, or inner support ring. The nozzle outer structure may comprise segments each of which has a single protrusion which is axially engageable with the outer support ring or, alternatively, a first and second protrusion which are arcuately and axially separated and which include axial openings therein whereby first and second protrusions on respective, arcuately adjacent nozzle segments have axial openings therein which are alignable with connector openings in the outer support ring and within each of such aligned openings a pin is receivable. The inner shroud may, likewise, comprise segments which, when assembled in operating configuration, have a 360 degree expanse.

Turbine nozzle/nozzle support structure

DOEpatents

Boyd, G.L.; Shaffer, J.E.

1997-01-07

An axial flow turbine`s nozzle/nozzle support structure is described having a cantilevered nozzle outer structure including an outer shroud and airfoil vanes extending radially inwardly therefrom, an inner shroud radially adjacent the inner end of the airfoil vanes and cooperatively disposed relative to the outer shroud to provide an annular fluid flow path, an inner and an outer support ring respectively arranged radially inside the inner shroud and axially adjacent a portion of the outer shroud, and pins extending through such portion and into the outer support ring. The inner support ring or inner shroud has a groove therein bounded by end walls for receiving and being axially abuttable with a locating projection from the adjacent airfoil vane, inner shroud, or inner support ring. The nozzle outer structure may comprise segments each of which has a single protrusion which is axially engageable with the outer support ring or, alternatively, a first and second protrusion which are arcuately and axially separated and which include axial openings therein whereby first and second protrusions on respective, arcuately adjacent nozzle segments have axial openings therein which are alignable with connector openings in the outer support ring and within each of such aligned openings a pin is receivable. The inner shroud may, likewise, comprise segments which, when assembled in operating configuration, have a 360 degree expanse. 6 figs.

Turbine nozzle/nozzle support structure

DOEpatents

Boyd, Gary L.; Shaffer, James E.

1996-01-01

An axial flow turbine's nozzle/nozzle support structure having a cantilevered nozzle outer structure including an outer shroud and airfoil vanes extending radially inwardly therefrom, an inner shroud radially adjacent the inner end of the airfoil vanes and cooperatively disposed relative to the outer shroud to provide an annular fluid flow path, an inner and an outer support ring respectively arranged radially inside the inner shroud and axially adjacent a portion of the outer shroud, and pins extending through such portion and into the outer support ring. The inner support ring or inner shroud has a groove therein bounded by end walls for receiving and being axially abuttable with a locating projection from the adjacent airfoil vane, inner shroud, or inner support ring. The nozzle outer structure may comprise segments each of which has a single protrusion which is axially engageable with the outer support ring or, alternatively, a first and second protrusion which are arcuately and axially separated and which include axial openings therein whereby first and second protrusions on respective, arcuately adjacent nozzle segments have axial openings therein which are alignable with connector openings in the outer support ring and within each of such aligned openings a pin is receivable. The inner shroud may, likewise, comprise segments which, when assembled in operating configuration, have a 360 degree expanse.

Turbine nozzle/nozzle support structure

DOEpatents

Boyd, G.L.; Shaffer, J.E.

1996-09-10

An axial flow turbine`s nozzle/nozzle support structure is described having a cantilevered nozzle outer structure including an outer shroud and airfoil vanes extending radially inwardly therefrom, an inner shroud radially adjacent the inner end of the airfoil vanes and cooperatively disposed relative to the outer shroud to provide an annular fluid flow path, an inner and an outer support ring respectively arranged radially inside the inner shroud and axially adjacent a portion of the outer shroud, and pins extending through such portion and into the outer support ring. The inner support ring or inner shroud has a groove therein bounded by end walls for receiving and being axially abuttable with a locating projection from the adjacent airfoil vane, inner shroud, or inner support ring. The nozzle outer structure may comprise segments each of which has a single protrusion which is axially engageable with the outer support ring or, alternatively, a first and second protrusion which are arcuately and axially separated and which include axial openings therein whereby first and second protrusions on respective, arcuately adjacent nozzle segments have axial openings therein which are alignable with connector openings in the outer support ring and within each of such aligned openings a pin is receivable. The inner shroud may, likewise, comprise segments which, when assembled in operating configuration, have a 360 degree expanse. 6 figs.

Turbine nozzle/nozzle support structure

DOEpatents

Boyd, Gary L.; Shaffer, James E.

1995-01-01

An axial flow turbine's nozzle/nozzle support structure having a cantilevered nozzle outer structure including an outer shroud and airfoil vanes extending radially inwardly therefrom, an inner shroud radially adjacent the inner end of the airfoil vanes and cooperatively disposed relative to the outer shroud to provide an annular fluid flow path, an inner and an outer support ring respectively arranged radially inside the inner shroud and axially adjacent a portion of the outer shroud, and pins extending through such portion and into the outer support ring. The inner support ring or inner shroud has a groove therein bounded by end walls for receiving and being axially abuttable with a locating projection from the adjacent airfoil vane, inner shroud, or inner support ring. The nozzle outer structure may comprise segments each of which has a single protrusion which is axially engageable with the outer support ring or, alternatively, a first and second protrusion which are arcuately and axially separated and which include axial openings therein whereby first and second protrusions on respective, arcuately adjacent nozzle segments have axial openings therein which are alignable with connector openings in the outer support ring and within each of such aligned openings a pin is receivable. The inner shroud may, likewise, comprise segments which, when assembled in operating configuration, have a 360 degree expanse.

Turbine nozzle/nozzle support structure

DOEpatents

Boyd, G.L.; Shaffer, J.E.

1995-08-15

An axial flow turbine`s nozzle/nozzle support structure is described having a cantilevered nozzle outer structure including an outer shroud and airfoil vanes extending radially inwardly therefrom, an inner shroud radially adjacent the inner end of the airfoil vanes and cooperatively disposed relative to the outer shroud to provide an annular fluid flow path, an inner and an outer support ring respectively arranged radially inside the inner shroud and axially adjacent a portion of the outer shroud, and pins extending through such portion and into the outer support ring. The inner support ring or inner shroud has a groove therein bounded by end walls for receiving and being axially abuttable with a locating projection from the adjacent airfoil vane, inner shroud, or inner support ring. The nozzle outer structure may comprise segments each of which has a single protrusion which is axially engageable with the outer support ring or, alternatively, a first and second protrusion which are arcuately and axially separated and which include axial openings therein whereby first and second protrusions on respective, arcuately adjacent nozzle segments have axial openings therein which are alignable with connector openings in the outer support ring and within each of such aligned openings a pin is receivable. The inner shroud may, likewise, comprise segments which, when assembled in operating configuration, have a 360 degree expanse. 6 figs.

Stuck fuel rod capping sleeve

DOEpatents

Gorscak, Donald A.; Maringo, John J.; Nilsen, Roy J.

1988-01-01

A stuck fuel rod capping sleeve to be used during derodding of spent fuel assemblies if a fuel rod becomes stuck in a partially withdrawn position and, thus, has to be severed. The capping sleeve has an inner sleeve made of a lower work hardening highly ductile material (e.g., Inconel 600) and an outer sleeve made of a moderately ductile material (e.g., 304 stainless steel). The inner sleeve may be made of an epoxy filler. The capping sleeve is placed on a fuel rod which is then severed by using a bolt cutter device. Upon cutting, the capping sleeve deforms in such a manner as to prevent the gross release of radioactive fuel material

Localization of the Norrie disease gene mRNA by in situ hybridization.

PubMed

Hartzer, M K; Cheng, M; Liu, X; Shastry, B S

1999-07-15

Norrie disease is a rare X-linked recessive neurodevelopmental disorder. The affected males manifest congenital blindness, which is often associated with hearing loss, mental retardation and psychiatric problems. Genetic linkage studies have localized the gene to the short arm of the X-chromosome and the gene has been isolated recently. The encoded protein is a member of the superfamily of growth factors containing a cystine knot motif and may be involved in cell adhesion and neurodevelopment. Molecular genetic analysis revealed a large number of missense, nonsense, deletion, and splice-site mutations among Norrie patients. In order to further determine the role of the Norrie disease gene, we studied the distribution pattern of its mRNA in the retina and in brain by in situ hybridization. The results show abundant hybridization signals in outer nuclear, inner nuclear, and ganglion cell layers of the retina in all three species (mice, rabbit, and human) examined. There was no significant expression in the vitreous body, lens, and rod outer segment. High expression levels were also observed in the cerebellar granular layer, hippocampus, olfactory bulb, cortex, and epithelium of the rabbit brain. These data suggest that the Norrie disease gene could play a critical role in the differentiation or maintenance of the differentiated state of the retina.

Adenovirally transduced bone marrow stromal cells differentiate into pigment epithelial cells and induce rescue effects in RCS rats.

PubMed

Arnhold, Stefan; Heiduschka, Peter; Klein, Helmut; Absenger, Yvonne; Basnaoglu, Serkan; Kreppel, Florian; Henke-Fahle, Sylvia; Kochanek, Stefan; Bartz-Schmidt, Karl-Ulrich; Addicks, Klaus; Schraermeyer, Ulrich

2006-09-01

To determine the potential of adenovirally transduced bone marrow stromal cells (BMSCs) to differentiate into retinal pigment epithelial-like cells and to evaluabe possible rescue effects after transplantation into the retinas of Royal College of Surgeons (RCS) rats. Through a high-capacity adenoviral vector expressing either green fluorescent protein (GFP) or pigment epithelial-derived factor (PEDF), rat MSCs were transduced in vitro before subretinal transplantation into Wistar rats or, alternatively, RCS rats. Two months after cell injection, the rats were killed and the eyes enucleated. The eyes were then investigated light microscopically or processed for electron microscopic investigations. Cell differentiation and integration were analyzed immunocytochemically using antibodies against cytokeratin and the tight junction protein ZO-1. Electroretinography was performed 16 days after injection of cells, to check whether a functional rescue could be detected. In vitro experiments in cocultured human MSCs and human RPE cells showed that MSCs adopted RPE-like characteristics. In grafting experiments, some rat MSCs integrate into the host RPE cell layer of Wistar and RCS rats, indicated by their hexagonal morphology. Subretinally transplanted cells express the epithelial marker cytokeratin and establish tight junctions with the host RPE cells. Furthermore, rescue effects can be demonstrated after grafting of vector-transduced and nontransduced MSCs in semithin sections of dystrophic retinas. Ultrastructurally, MSCs can be detected on top of host RPE and in close contact with photoreceptor outer segments phagocytosing rod outer segments. Taken together, these results raise the possibility that MSCs have the potency to replace diseased RPE cells and deliver therapeutic proteins into the subretinal space to protect photoreceptor cells from degeneration.

Detection and visualization of endoleaks in CT data for monitoring of thoracic and abdominal aortic aneurysm stents

NASA Astrophysics Data System (ADS)

Lu, J.; Egger, J.; Wimmer, A.; Großkopf, S.; Freisleben, B.

2008-03-01

In this paper we present an efficient algorithm for the segmentation of the inner and outer boundary of thoratic and abdominal aortic aneurysms (TAA & AAA) in computed tomography angiography (CTA) acquisitions. The aneurysm segmentation includes two steps: first, the inner boundary is segmented based on a grey level model with two thresholds; then, an adapted active contour model approach is applied to the more complicated outer boundary segmentation, with its initialization based on the available inner boundary segmentation. An opacity image, which aims at enhancing important features while reducing spurious structures, is calculated from the CTA images and employed to guide the deformation of the model. In addition, the active contour model is extended by a constraint force that prevents intersections of the inner and outer boundary and keeps the outer boundary at a distance, given by the thrombus thickness, to the inner boundary. Based upon the segmentation results, we can measure the aneurysm size at each centerline point on the centerline orthogonal multiplanar reformatting (MPR) plane. Furthermore, a 3D TAA or AAA model is reconstructed from the set of segmented contours, and the presence of endoleaks is detected and highlighted. The implemented method has been evaluated on nine clinical CTA data sets with variations in anatomy and location of the pathology and has shown promising results.

Segmented Mirror Image Degradation Due to Surface Dust, Alignment and Figure

NASA Technical Reports Server (NTRS)

Schreur, Julian J.

1999-01-01

In 1996 an algorithm was developed to include the effects of surface roughness in the calculation of the point spread function of a telescope mirror. This algorithm has been extended to include the effects of alignment errors and figure errors for the individual elements, and an overall contamination by surface dust. The final algorithm builds an array for a guard-banded pupil function of a mirror that may or may not have a central hole, a central reflecting segment, or an outer ring of segments. The central hole, central reflecting segment, and outer ring may be circular or polygonal, and the outer segments may have trimmed comers. The modeled point spread functions show that x-tilt and y-tilt, or the corresponding R-tilt and theta-tilt for a segment in an outer ring, is readily apparent for maximum wavefront errors of 0.1 lambda. A similar sized piston error is also apparent, but integral wavelength piston errors are not. Severe piston error introduces a focus error of the opposite sign, so piston could be adjusted to compensate for segments with varying focal lengths. Dust affects the image principally by decreasing the Strehl ratio, or peak intensity of the image. For an eight-meter telescope a 25% coverage by dust produced a scattered light intensity of 10(exp -9) of the peak intensity, a level well below detectability.

cAMP controls rod photoreceptor sensitivity via multiple targets in the phototransduction cascade

PubMed Central

Astakhova, Luba A.; Samoiliuk, Evgeniia V.; Govardovskii, Victor I.

2012-01-01

In early studies, both cyclic AMP (cAMP) and cGMP were considered as potential secondary messengers regulating the conductivity of the vertebrate photoreceptor plasma membrane. Later discovery of the cGMP specificity of cyclic nucleotide–gated channels has shifted attention to cGMP as the only secondary messenger in the phototransduction cascade, and cAMP is not considered in modern schemes of phototransduction. Here, we report evidence that cAMP may also be involved in regulation of the phototransduction cascade. Using a suction pipette technique, we recorded light responses of isolated solitary rods from the frog retina in normal solution and in the medium containing 2 µM of adenylate cyclase activator forskolin. Under forskolin action, flash sensitivity rose more than twofold because of a retarded photoresponse turn-off. The same concentration of forskolin lead to a 2.5-fold increase in the rod outer segment cAMP, which is close to earlier reported natural day/night cAMP variations. Detailed analysis of cAMP action on the phototransduction cascade suggests that several targets are affected by cAMP increase: (a) basal dark phosphodiesterase (PDE) activity decreases; (b) at the same intensity of light background, steady background-induced PDE activity increases; (c) at light backgrounds, guanylate cyclase activity at a given fraction of open channels is reduced; and (d) the magnitude of the Ca2+ exchanger current rises 1.6-fold, which would correspond to a 1.6-fold elevation of [Ca2+]in. Analysis by a complete model of rod phototransduction suggests that an increase of [Ca2+]in might also explain effects (b) and (c). The mechanism(s) by which cAMP could regulate [Ca2+]in and PDE basal activity is unclear. We suggest that these regulations may have adaptive significance and improve the performance of the visual system when it switches between day and night light conditions. PMID:23008435

Loss of retinoschisin (RS1) cell surface protein in maturing mouse rod photoreceptors elevates the luminance threshold for light-driven translocation of transducin but not arrestin.

PubMed

Ziccardi, Lucia; Vijayasarathy, Camasamudram; Bush, Ronald A; Sieving, Paul A

2012-09-19

Loss of retinoschisin (RS1) in Rs1 knock-out (Rs1-KO) retina produces a post-photoreceptor phenotype similar to X-linked retinoschisis in young males. However, Rs1 is expressed strongly in photoreceptors, and Rs1-KO mice have early reduction in the electroretinogram a-wave. We examined light-activated transducin and arrestin translocation in young Rs1-KO mice as a marker for functional abnormalities in maturing rod photoreceptors. We found a progressive reduction in luminance threshold for transducin translocation in wild-type (WT) retinas between postnatal days P18 and P60. At P21, the threshold in Rs1-KO retinas was 10-fold higher than WT, but it decreased to <2.5-fold higher by P60. Light-activated arrestin translocation and re-translocation of transducin in the dark were not affected. Rs1-KO rod outer segment (ROS) length was significantly shorter than WT at P21 but was comparable with WT at P60. These findings suggested a delay in the structural and functional maturation of Rs1-KO ROS. Consistent with this, transcription factors CRX and NRL, which are fundamental to maturation of rod protein expression, were reduced in ROS of Rs1-KO mice at P21 but not at P60. Expression of transducin was 15-30% lower in P21 Rs1-KO ROS and transducin GTPase hydrolysis was nearly twofold faster, reflecting a 1.7- to 2.5-fold increase in RGS9 (regulator of G-protein signaling) level. Transduction protein expression and activity levels were similar to WT at P60. Transducin translocation threshold elevation indicates photoreceptor functional abnormalities in young Rs1-KO mice. Rapid reduction in threshold coupled with age-related changes in transduction protein levels and transcription factor expression are consistent with delayed maturation of Rs1-KO photoreceptors.

Targeted Ablation of the Pde6h Gene in Mice Reveals Cross-species Differences in Cone and Rod Phototransduction Protein Isoform Inventory*

PubMed Central

Brennenstuhl, Christina; Tanimoto, Naoyuki; Burkard, Markus; Wagner, Rebecca; Bolz, Sylvia; Trifunovic, Dragana; Kabagema-Bilan, Clement; Paquet-Durand, Francois; Beck, Susanne C.; Huber, Gesine; Seeliger, Mathias W.; Ruth, Peter; Wissinger, Bernd; Lukowski, Robert

2015-01-01

Phosphodiesterase-6 (PDE6) is a multisubunit enzyme that plays a key role in the visual transduction cascade in rod and cone photoreceptors. Each type of photoreceptor utilizes discrete catalytic and inhibitory PDE6 subunits to fulfill its physiological tasks, i.e. the degradation of cyclic guanosine-3′,5′-monophosphate at specifically tuned rates and kinetics. Recently, the human PDE6H gene was identified as a novel locus for autosomal recessive (incomplete) color blindness. However, the three different classes of cones were not affected to the same extent. Short wave cone function was more preserved than middle and long wave cone function indicating that some basic regulation of the PDE6 multisubunit enzyme was maintained albeit by a unknown mechanism. To study normal and disease-related functions of cone Pde6h in vivo, we generated Pde6h knock-out (Pde6h−/−) mice. Expression of PDE6H in murine eyes was restricted to both outer segments and synaptic terminals of short and long/middle cone photoreceptors, whereas Pde6h−/− retinae remained PDE6H-negative. Combined in vivo assessment of retinal morphology with histomorphological analyses revealed a normal overall integrity of the retinal organization and an unaltered distribution of the different cone photoreceptor subtypes upon Pde6h ablation. In contrast to human patients, our electroretinographic examinations of Pde6h−/− mice suggest no defects in cone/rod-driven retinal signaling and therefore preserved visual functions. To this end, we were able to demonstrate the presence of rod PDE6G in cones indicating functional substitution of PDE6. The disparities between human and murine phenotypes caused by mutant Pde6h/PDE6H suggest species-to-species differences in the vulnerability of biochemical and neurosensory pathways of the visual signal transduction system. PMID:25739440

Conidial Hydrophobins of Aspergillus fumigatus

PubMed Central

Paris, Sophie; Debeaupuis, Jean-Paul; Crameri, Reto; Carey, Marilyn; Charlès, Franck; Prévost, Marie Christine; Schmitt, Christine; Philippe, Bruno; Latgé, Jean Paul

2003-01-01

The surface of Aspergillus fumigatus conidia, the first structure recognized by the host immune system, is covered by rodlets. We report that this outer cell wall layer contains two hydrophobins, RodAp and RodBp, which are found as highly insoluble complexes. The RODA gene was previously characterized, and ΔrodA conidia do not display a rodlet layer (N. Thau, M. Monod, B. Crestani, C. Rolland, G. Tronchin, J. P. Latgé, and S. Paris, Infect. Immun. 62:4380-4388, 1994). The RODB gene was cloned and disrupted. RodBp was highly homologous to RodAp and different from DewAp of A. nidulans. ΔrodB conidia had a rodlet layer similar to that of the wild-type conidia. Therefore, unlike RodAp, RodBp is not required for rodlet formation. The surface of ΔrodA conidia is granular; in contrast, an amorphous layer is present at the surface of the conidia of the ΔrodA ΔrodB double mutant. These data show that RodBp plays a role in the structure of the conidial cell wall. Moreover, rodletless mutants are more sensitive to killing by alveolar macrophages, suggesting that RodAp or the rodlet structure is involved in the resistance to host cells. PMID:12620846

Heat Transfer Enhancement By Three-Dimensional Surface Roughness Technique In Nuclear Fuel Rod Bundles

NASA Astrophysics Data System (ADS)

Najeeb, Umair

This thesis experimentally investigates the enhancement of single-phase heat transfer, frictional loss and pressure drop characteristics in a Single Heater Element Loop Tester (SHELT). The heater element simulates a single fuel rod for Pressurized Nuclear reactor. In this experimental investigation, the effect of the outer surface roughness of a simulated nuclear rod bundle was studied. The outer surface of a simulated fuel rod was created with a three-dimensional (Diamond-shaped blocks) surface roughness. The angle of corrugation for each diamond was 45 degrees. The length of each side of a diamond block is 1 mm. The depth of each diamond block was 0.3 mm. The pitch of the pattern was 1.614 mm. The simulated fuel rod had an outside diameter of 9.5 mm and wall thickness of 1.5 mm and was placed in a test-section made of 38.1 mm inner diameter, wall thickness 6.35 mm aluminum pipe. The Simulated fuel rod was made of Nickel 200 and Inconel 625 materials. The fuel rod was connected to 10 KW DC power supply. The Inconel 625 material of the rod with an electrical resistance of 32.3 kO was used to generate heat inside the test-section. The heat energy dissipated from the Inconel tube due to the flow of electrical current flows into the working fluid across the rod at constant heat flux conditions. The DI water was employed as working fluid for this experimental investigation. The temperature and pressure readings for both smooth and rough regions of the fuel rod were recorded and compared later to find enhancement in heat transfer coefficient and increment in the pressure drops. Tests were conducted for Reynold's Numbers ranging from 10e4 to 10e5. Enhancement in heat transfer coefficient at all Re was recorded. The maximum heat transfer co-efficient enhancement recorded was 86% at Re = 4.18e5. It was also observed that the pressure drop and friction factor increased by 14.7% due to the increased surface roughness.

Microstructure and Mechanical Properties of Long Ti-6Al-4V Rods Additively Manufactured by Selective Electron Beam Melting Out of a Deep Powder Bed and the Effect of Subsequent Hot Isostatic Pressing

NASA Astrophysics Data System (ADS)

Lu, S. L.; Tang, H. P.; Ning, Y. P.; Liu, N.; StJohn, D. H.; Qian, M.

2015-09-01

An array of eight long Ti-6Al-4V rods (diameter: 12 mm; height: 300 mm) have been additively manufactured, vertically and perpendicular to the powder bed, by selective electron beam melting (SEBM). The purpose was to identify and understand the challenges of fabricating Ti-6Al-4V samples or parts from a deep powder bed (more than 200-mm deep) by SEBM and the necessity of applying post heat treatment. The resulting microstructure and mechanical properties of these Ti-6Al-4V rods were characterized along their building ( i.e., axial) direction by dividing each rod into three segments (top, middle, and bottom), both before ( i.e., as-built) and after hot isostatic pressing (HIP). The as-built microstructure of each rod was inhomogeneous; it was coarsest in the top segment, which showed a near equilibrium α- β lamellar structure, and finest in the bottom segment, which featured a non-equilibrium mixed structure. The tensile properties varied along the rod axis, especially the ductility, but all tensile properties met the requirements specified by ASTM F3001-14. HIP increased the relative density from 99.03 pct of the theoretical density (TD) to 99.90 pct TD and homogenized the microstructure thereby leading to highly consistent tensile properties along the rod axis. The temperature of the stainless steel substrate used in the powder bed was monitored. The as-built inhomogeneous microstructure is attributed to the temperature gradient in the deep powder bed. Post heat treatment is thus necessary for Ti-6Al-4V samples or parts manufactured from a deep powder bed by SEBM. This differs from the additive manufacturing of small samples or parts from a shallow powder bed (less than 100-mm deep) by SEBM.

Alterations of the outer retina in non-arteritic anterior ischaemic optic neuropathy detected using spectral-domain optical coherence tomography.

PubMed

Ackermann, Philipp; Brachert, Maike; Albrecht, Philipp; Ringelstein, Marius; Finis, David; Geerling, Gerd; Aktas, Orhan; Guthoff, Rainer

2017-07-01

A characteristic disease pattern may be reflected by retinal layer thickness changes in non-arteritic anterior ischaemic optic neuropathy measured using spectraldomain optical coherence tomography. Retinal layer segmentation is enabled by advanced software. In this study, retinal layer thicknesses in acute and chronic non-arteritic anterior ischaemic optic neuropathy were compared. A single-centre cross-sectional analysis was used. A total of 27 patients (20 age-matched healthy eyes) were included: 14 with acute (<7 days) and 13 patients with chronic non-arteritic anterior ischaemic optic neuropathy. Macular volume and 12° peripapillary ring optical coherence tomography scans were used. The peripapillary thicknesses of the following layers were determined by manual segmentation: retinal nerve fibres, ganglion cells + inner plexiform layer, inner nuclear layer + outer plexiform layer, outer nuclear layer + inner segments of the photoreceptors and outer segments of the photoreceptors to Bruch's membrane. Macular retinal layer thicknesses were automatically determined in volume cubes centred on the fovea. Peripapillary retinal swelling in acute nonarteritic anterior ischaemic optic neuropathy was attributable to retinal nerve fibre layer, ganglion cell layer/inner plexiform layer and outer nuclear layer/segments of the photoreceptors thickening. In chronic cases, peripapillary retinal nerve fibre layer, macular ganglion cell layer and inner plexiform layer thinning were observed. In acute non-arteritic anterior ischaemic optic neuropathy, the inner and outer peripapillary retinal layers are affected by thickness changes. In chronic cases, atrophy of the ganglion cells and their axons and dendrites is evident by inner retinal layer thinning. © 2017 Royal Australian and New Zealand College of Ophthalmologists.

System for supporting a bundled tube fuel injector within a combustor

DOE Office of Scientific and Technical Information (OSTI.GOV)

LeBegue, Jeffrey Scott; Melton, Patrick Benedict; Westmoreland, III, James Harold

A combustor includes an end cover having an outer side and an inner side, an outer barrel having a forward end that is adjacent to the inner side of the end cover and an aft end that is axially spaced from the forward end. An inner barrel is at least partially disposed concentrically within the outer barrel and is fixedly connected to the outer barrel. A fluid conduit extends downstream from the end cover. A first bundled tube fuel injector segment is disposed concentrically within the inner barrel. The bundled tube fuel injector segment includes a fuel plenum that ismore » in fluid communication with the fluid conduit and a plurality of parallel tubes that extend axially through the fuel plenum. The bundled tube fuel injector segment is fixedly connected to the inner barrel.« less

The saturation of monochromatic lights obliquely incident on the retina.

PubMed Central

Alpern, M; Tamaki, R

1983-01-01

Foveal dark-adaptation undertaken to test the hypothesis that the excitation of rods causes the desaturation of 'yellow' lights in a 1 degree field traversing the margin of the pupil, fails to exclude that possibility. The desaturation is largest for a 1 degree outside diameter annular test, is still measurable with a 0.5 degree circular disk, but disappears for a 0.29 degree disk. The supersaturation of obliquely incident 501.2 nm test light follows the opposite pattern; it disappears with an annulus and is largest for a 0.29 degree circular field. It is unlikely that rods replace short-wave sensitive cones in the trichromatic match of an obliquely incident test with normally incident primaries. If rods as well as all three cones species are involved, the matches might not be trichromatic in the strong sense. Grassmann's law of scalar multiplication was tested and shown not to hold for the match of an obliquely incident test with normally incident primaries, though it remains valid whenever, both primaries and test strike the retina at the same angle of incidence (independent of that angle). The result in section 3 (above) cannot be due to rod intrusion. It persists (and becomes more conspicuous) on backgrounds (4.0 log scotopic td) which saturate rods. Moreover obliquely incident 'yellow' lights remain desaturated in intervals in the dark after a full bleach, whilst the test field is below rod threshold. The amount of desaturation does not differ appreciably from that normally found. The assumption of the unified theory of Alpern, Kitahara & Tamaki (1983) that the outer segments of only a single set of three cone species (with acceptance angles wide enough to include the entire exit pupil) contain the visual pigments absorbing both the normally incident primaries and the obliquely incident test is disproved by these results. Failure of Grassmann's law is most conspicuous under the conditions for which the changes in saturation upon changing from normal to oblique incidence are greatest and least when the saturation changes are the smallest. Either all unified theories of the Stiles-Crawford effects are wrong or all the effects of oblique incidence operate at a stage in the visual process at which the effects of radiation of different wave-lengths are no longer compounded by the simple linear laws. PMID:6875976

Segmented trapped vortex cavity

NASA Technical Reports Server (NTRS)

Grammel, Jr., Leonard Paul (Inventor); Pennekamp, David Lance (Inventor); Winslow, Jr., Ralph Henry (Inventor)

2010-01-01

An annular trapped vortex cavity assembly segment comprising includes a cavity forward wall, a cavity aft wall, and a cavity radially outer wall there between defining a cavity segment therein. A cavity opening extends between the forward and aft walls at a radially inner end of the assembly segment. Radially spaced apart pluralities of air injection first and second holes extend through the forward and aft walls respectively. The segment may include first and second expansion joint features at distal first and second ends respectively of the segment. The segment may include a forward subcomponent including the cavity forward wall attached to an aft subcomponent including the cavity aft wall. The forward and aft subcomponents include forward and aft portions of the cavity radially outer wall respectively. A ring of the segments may be circumferentially disposed about an axis to form an annular segmented vortex cavity assembly.

Interaction of Extracellular Domain 2 of the Human Retina-specific ATP-binding Cassette Transporter (ABCA4) with All-trans-retinal*

PubMed Central

Biswas-Fiss, Esther E.; Kurpad, Deepa S.; Joshi, Kinjalben; Biswas, Subhasis B.

2010-01-01

The retina-specific ATP-binding cassette (ABC) transporter, ABCA4, is essential for transport of all-trans-retinal from the rod outer segment discs in the retina and is associated with a broad range of inherited retinal diseases, including Stargardt disease, autosomal recessive cone rod dystrophy, and fundus flavimaculatus. A unique feature of the ABCA subfamily of ABC transporters is the presence of highly conserved, long extracellular loops or domains (ECDs) with unknown function. The high degree of sequence conservation and mapped disease-associated mutations in these domains suggests an important physiological significance. Conformational analysis using CD spectroscopy of purified, recombinant ECD2 protein demonstrated that it has an ordered and stable structure composed of 27 ± 3% α-helix, 20 ± 3% β-pleated sheet, and 53 ± 3% coil. Significant conformational changes were observed in disease-associated mutant proteins. Using intrinsic tryptophan fluorescence emission spectrum of ECD2 polypeptide and fluorescence anisotropy, we have demonstrated that this domain specifically interacts with all-trans-retinal. Furthermore, the retinal interaction appeared preferential for the all-trans-isomer and was directly measurable through fluorescence anisotropy analysis. Our results demonstrate that the three macular degeneration-associated mutations lead to significant changes in the secondary structure of the ECD2 domain of ABCA4, as well as in its interaction with all-trans-retinal. PMID:20404325

Parallel Operation of Multiple Closely Spaced Small Aspect Ratio Rod Pinches

DOE PAGES

Harper-Slaboszewicz, Victor J.; Leckbee, Joshua; Bennett, Nichelle; ...

2014-12-10

A series of simulations and experiments to resolve questions about the operation of arrays of closely spaced small aspect ratio rod pinches has been performed. Design and post-shot analysis of the experimental results are supported by 3D particle-in-cell simulations. Both simulations and experiments support these conclusions. Penetration of current to the interior of the array appears to be efficient, as the current on the center rods is essentially equal to the current on the outer rods. Current loss in the feed due to the formation of magnetic nulls was avoided in these experiments by design of the feed surface ofmore » the cathode and control of the gap to keep the electric fields on the cathode below the emission threshold. Some asymmetry in the electron flow to the rod was observed, but the flow appeared to symmetrize as it reached the end of the rod. Interaction between the rod pinches can be controlled to allow the stable and consistent operation of arrays of rod pinches.« less

Uncoordinated (UNC)119: coordinating the trafficking of myristoylated proteins.

PubMed

Constantine, Ryan; Zhang, Houbin; Gerstner, Cecilia D; Frederick, Jeanne M; Baehr, Wolfgang

2012-12-15

The mechanism by which myristoylated proteins are targeted to specific subcellular membrane compartments is poorly understood. Two novel acyl-binding proteins, UNC119A and UNC119B, have been shown recently to function as chaperones/co-factors in the transport of myristoylated G protein α-subunits and src-type tyrosine kinases. UNC119 polypeptides feature an immunoglobulin-like β-sandwich fold that forms a hydrophobic pocket capable of binding lauroyl (C12) and myristoyl (C14) side chains. UNC119A in rod photoreceptors facilitates the transfer of transducin α subunits (Tα) from inner segment to outer segment membranes by forming an intermediate diffusible UNC119-Tα complex. Similar complexes are formed in other sensory neurons, as the G proteins ODR-3 and GPA-13 in Caenorhabditis elegans unc-119 mutants traffic inappropriately. UNC119B knockdown in IMCD3 cells prevents trafficking ofmyristoylated nephrocystin-3 (NPHP3), a protein associated with nephronophthisis, to cilia. Further, UNC119A was shown to transport myristoylated src-type tyrosine kinases to cell membranes and to affect T-cell receptor (TCR) and interleukin-5 receptor (IL-5R) activities. These interactions establish UNC119 polypeptides as novel lipid-binding chaperones with specificity for a diverse subset of myristoylated proteins. Copyright © 2012 Elsevier Ltd. All rights reserved.

Uncoordinated (UNC)119: Coordinating the Trafficking of Myristoylated Proteins

PubMed Central

Constantine, Ryan; Zhang, Houbin; Gerstner, Cecilia D.; Frederick, Jeanne M.; Baehr, Wolfgang

2012-01-01

The mechanism by which myristoylated proteins are targeted to specific subcellular membrane compartments is poorly understood. Two novel acyl-binding proteins, UNC119A and UNC119B, have been shown recently to function as chaperones/co-factors in the transport of myristoylated G protein α-subunits and src-type tyrosine kinases. UNC119 polypeptides feature an immunoglobulin-like β-sandwich fold that forms a hydrophobic pocket capable of binding lauroyl (C12) and myristoyl (C14) side chains. UNC119A in rod photoreceptors facilitates the transfer of transducin α subunits (Tα) from inner segment to outer segment membranes by forming an intermediate diffusible UNC119-Tα complex. Similar complexes are formed in other sensory neurons, as the G proteins ODR-3 and GPA-13 in C. elegans unc-119 mutants traffic inappropriately. UNC119B knockdown in IMCD3 cells prevents trafficking of myristoylated nephrocystin-3 (NPHP3), a protein associated with nephronophthisis, to cilia. Further, UNC119A was shown to transpot myristoylated src-type tyrosine kinases to cell membranes and to affect T-cell receptor (TCR) and interleukin-5 receptor (IL-5R) activities. These interactions establish UNC119 polypeptides as novel lipid-binding chaperones with specificity for a diverse subset of myristoylated proteins. PMID:23000199

Wedge edge ceramic combustor tile

DOEpatents

Shaffer, J.E.; Holsapple, A.C.

1997-06-10

A multipiece combustor has a portion thereof being made of a plurality of ceramic segments. Each of the plurality of ceramic segments have an outer surface and an inner surface. Each of the plurality of ceramic segments have a generally cylindrical configuration and including a plurality of joints. The joints define joint portions, a first portion defining a surface being skewed to the outer surface and the inner surface. The joint portions have a second portion defining a surface being skewed to the outer surface and the inner surface. The joint portions further include a shoulder formed intermediate the first portion and the second portion. The joints provide a sealing interlocking joint between corresponding ones of the plurality of ceramic segments. Thus, the multipiece combustor having the plurality of ceramic segment with the plurality of joints reduces the physical size of the individual components and the degradation of the surface of the ceramic components in a tensile stress zone is generally eliminated reducing the possibility of catastrophic failures. 7 figs.

Wedge edge ceramic combustor tile

DOEpatents

Shaffer, James E.; Holsapple, Allan C.

1997-01-01

A multipiece combustor has a portion thereof being made of a plurality of ceramic segments. Each of the plurality of ceramic segments have an outer surface and an inner surface. Each of the plurality of ceramic segments have a generally cylindrical configuration and including a plurality of joints. The joints define joint portions, a first portion defining a surface being skewed to the outer surface and the inner surface. The joint portions have a second portion defining a surface being skewed to the outer surface and the inner surface. The joint portions further include a shoulder formed intermediate the first portion and the second portion. The joints provide a sealing interlocking joint between corresponding ones of the plurality of ceramic segments. Thus, the multipiece combustor having the plurality of ceramic segment with the plurality of joints reduces the physical size of the individual components and the degradation of the surface of the ceramic components in a tensile stress zone is generally eliminated reducing the possibility of catastrophic failures.

Quantification of photoreceptor layer thickness in different macular pathologies using ultrahigh-resolution optical coherence tomography

NASA Astrophysics Data System (ADS)

Drexler, Wolfgang; Hermann, Boris; Unterhuber, Angelika; Sattmann, Harald; Wirtitsch, Matthias; Stur, Michael; Scholda, Christoph; Ergun, Erdem; Anger, Elisabeth; Ko, Tony H.; Schubert, Christian; Ahnelt, Peter K.; Fujimoto, James G.; Fercher, Adolf F.

2004-07-01

In vivo ultrahigh resolution ophthalmic OCT has been performed in more than 300 eyes of 200 patients with several retinal pathologies, demonstrating unprecedented visualization of all major intraretinal layers, in particular the photoreceptor layer. Visualization as well as quantification of the inner and outer segment of the photoreceptor layer especially in the foveal region has been acvhieved. In normal subjects the photoreceptor layer thickness in the center of the fovea is about of 90 μm, approximately equally distributed to the inner and the outer photoreceptor segment. In the parafoveal region this thickness is reduced to ~50 μm (~30 μm for the inner and ~20 μm for the outer segment). This is in good agreement with well known increase of cone outer segments in the central foveal region. Photoreceptor layer impairment in different macular pathologies like macular hole, central serous chorioretinopathy, age related macular degeneration, foveomacular dystrophies, Stargardt dystrophy as well as retinitis pigmentosa has been investigated. Photoreceptor layer loss significantly correlated with visual acuity (R2 = 0.6, p < 0.001) and microperimetry findings for the first time in 22 eyes with Stargardt dystrophy. Visualization and quantification of photoreceptor inner and outer segment using ultrahigh resolution OCT has the potential to improve early ophthalmic diagnosis, contributes to a better understanding of pathogenesis of retinal diseases as well as might have impact in the development and monitoring of novel therapy approaches.

Development of fast cooling pulsed magnets at the Wuhan National High Magnetic Field Center.

PubMed

Peng, Tao; Sun, Quqin; Zhao, Jianlong; Jiang, Fan; Li, Liang; Xu, Qiang; Herlach, Fritz

2013-12-01

Pulsed magnets with fast cooling channels have been developed at the Wuhan National High Magnetic Field Center. Between the inner and outer sections of a coil wound with a continuous length of CuNb wire, G10 rods with cross section 4 mm × 5 mm were inserted as spacers around the entire circumference, parallel to the coil axis. The free space between adjacent rods is 6 mm. The liquid nitrogen flows freely in the channels between these rods, and in the direction perpendicular to the rods through grooves provided in the rods. For a typical 60 T pulsed magnetic field with pulse duration of 40 ms, the cooling time between subsequent pulses is reduced from 160 min to 35 min. Subsequently, the same technology was applied to a 50 T magnet with 300 ms pulse duration. The cooling time of this magnet was reduced from 480 min to 65 min.

Rod electrical coupling is controlled by a circadian clock and dopamine in mouse retina

PubMed Central

Jin, Nan Ge; Chuang, Alice Z; Masson, Philippe J; Ribelayga, Christophe P

2015-01-01

Key points Rod photoreceptors play a key role in vision in dim light; in the mammalian retina, although rods are anatomically connected or coupled by gap junctions, a type of electrical synapse, the functional importance and regulation of rod coupling has remained elusive. We have developed a new technique in the mouse: perforated patch-clamp recording of rod inner segments in isolated intact retinae maintained by superfusion. We find that rod electrical coupling is controlled by a circadian clock and dopamine, and is weak during the day and stronger at night. The results also indicate that the signal-to-noise ratio for a dim light response is increased at night because of coupling. Our observations will provide a framework for understanding the daily variations in human vision as well as the basis of specific retinal malfunctions. Abstract Rod single-photon responses are critical for vision in dim light. Electrical coupling via gap junction channels shapes the light response properties of vertebrate photoreceptors, but the regulation of rod coupling and its impact on the single-photon response have remained unclear. To directly address these questions, we developed a perforated patch-clamp recording technique and recorded from single rod inner segments in isolated intact neural mouse retinae, maintained by superfusion. Experiments were conducted at different times of the day or under constant environmental conditions, at different times across the circadian cycle. We show that rod electrical coupling is regulated by a circadian clock and dopamine, so that coupling is weak during the day and strong at night. Altogether, patch-clamp recordings of single-photon responses in mouse rods, tracer coupling, receptive field measurements and pharmacological manipulations of gap junction and dopamine receptor activity provide compelling evidence that rod coupling is modulated in a circadian manner. These data are consistent with computer modelling. At night, single-photon responses are smaller due to coupling, but the signal-to-noise ratio for a dim (multiphoton) light response is increased at night because of signal averaging between coupled rods. PMID:25616058

Influence of Arrestin on the Photodecay of Bovine Rhodopsin.

PubMed

Chatterjee, Deep; Eckert, Carl Elias; Slavov, Chavdar; Saxena, Krishna; Fürtig, Boris; Sanders, Charles R; Gurevich, Vsevolod V; Wachtveitl, Josef; Schwalbe, Harald

2015-11-09

Continued activation of the photocycle of the dim-light receptor rhodopsin leads to the accumulation of all-trans-retinal in the rod outer segments (ROS). This accumulation can damage the photoreceptor cell. For retinal homeostasis, deactivation processes are initiated in which the release of retinal is delayed. One of these processes involves the binding of arrestin to rhodopsin. Here, the interaction of pre-activated truncated bovine visual arrestin (Arr(Tr)) with rhodopsin in 1,2-diheptanoyl-sn-glycero-3-phosphocholine (DHPC) micelles is investigated by solution NMR techniques and flash photolysis spectroscopy. Our results show that formation of the rhodopsin-arrestin complex markedly influences partitioning in the decay kinetics of rhodopsin, which involves the simultaneous formation of a meta II and a meta III state from the meta I state. Binding of Arr(Tr) leads to an increase in the population of the meta III state and consequently to an approximately twofold slower release of all-trans-retinal from rhodopsin. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Laser pulse detector

DOEpatents

Mashburn, D.N.; Akerman, M.A.

1979-08-13

A laser pulse detector is provided which is small and inexpensive and has the capability of detecting laser light of any wavelength with fast response (less than 5 nanoseconds rise time). The laser beam is focused onto the receiving end of a graphite rod coaxially mounted within a close-fitting conductive, open-end cylindrical housing so that ablation and electric field breakdown of the resulting plasma occurs due to a bias potential applied between the graphite rod and housing. The pulse produced by the breakdown is transmitted through a matched impedance coaxial cable to a recording device. The cable is connected with its central lead to the graphite rod and its outer conductor to the housing.

Laser pulse detector

DOEpatents

Mashburn, Douglas N.; Akerman, M. Alfred

1981-01-01

A laser pulse detector is provided which is small and inexpensive and has the capability of detecting laser light of any wavelength with fast response (less than 5 nanoseconds rise time). The laser beam is focused onto the receiving end of a graphite rod coaxially mounted within a close-fitting conductive, open-end cylindrical housing so that ablation and electric field breakdown of the resulting plasma occurs due to a bias potential applied between the graphite rod and housing. The pulse produced by the breakdown is transmitted through a matched impedance coaxial cable to a recording device. The cable is connected with its central lead to the graphite rod and its outer conductor to the housing.

Impact assisted segmented cutterhead

DOEpatents

Morrell, Roger J.; Larson, David A.; Ruzzi, Peter L.

1992-01-01

An impact assisted segmented cutterhead device is provided for cutting various surfaces from coal to granite. The device comprises a plurality of cutting bit segments deployed in side by side relationship to form a continuous cutting face and a plurality of impactors individually associated with respective cutting bit segments. An impactor rod of each impactor connects that impactor to the corresponding cutting bit segment. A plurality of shock mounts dampening the vibration from the associated impactor. Mounting brackets are used in mounting the cutterhead to a base machine.

In Vivo Precision of Digital Topological Skeletonization Based Individual Trabecula Segmentation (ITS) Analysis of Trabecular Microstructure at the Distal Radius and Tibia by HR-pQCT.

PubMed

Zhou, Bin; Zhang, Zhendong; Wang, Ji; Yu, Y Eric; Liu, Xiaowei Sherry; Nishiyama, Kyle K; Rubin, Mishaela R; Shane, Elizabeth; Bilezikian, John P; Guo, X Edward

2016-06-01

Trabecular plate and rod microstructure plays a dominant role in the apparent mechanical properties of trabecular bone. With high-resolution computed tomography (CT) images, digital topological analysis (DTA) including skeletonization and topological classification was applied to transform the trabecular three-dimensional (3D) network into surface and curve skeletons. Using the DTA-based topological analysis and a new reconstruction/recovery scheme, individual trabecula segmentation (ITS) was developed to segment individual trabecular plates and rods and quantify the trabecular plate- and rod-related morphological parameters. High-resolution peripheral quantitative computed tomography (HR-pQCT) is an emerging in vivo imaging technique to visualize 3D bone microstructure. Based on HR-pQCT images, ITS was applied to various HR-pQCT datasets to examine trabecular plate- and rod-related microstructure and has demonstrated great potential in cross-sectional and longitudinal clinical applications. However, the reproducibility of ITS has not been fully determined. The aim of the current study is to quantify the precision errors of ITS plate-rod microstructural parameters. In addition, we utilized three different frequently used contour techniques to separate trabecular and cortical bone and to evaluate their effect on ITS measurements. Overall, good reproducibility was found for the standard HR-pQCT parameters with precision errors for volumetric BMD and bone size between 0.2%-2.0%, and trabecular bone microstructure between 4.9%-6.7% at the radius and tibia. High reproducibility was also achieved for ITS measurements using all three different contour techniques. For example, using automatic contour technology, low precision errors were found for plate and rod trabecular number (pTb.N, rTb.N, 0.9% and 3.6%), plate and rod trabecular thickness (pTb.Th, rTb.Th, 0.6% and 1.7%), plate trabecular surface (pTb.S, 3.4%), rod trabecular length (rTb.ℓ, 0.8%), and plate-plate junction density (P-P Junc.D, 2.3%) at the tibia. The precision errors at the radius were similar to those at the tibia. In addition, precision errors were affected by the contour technique. At the tibia, precision error by the manual contour method was significantly different from automatic and standard contour methods for pTb.N, rTb.N and rTb.Th. Precision error using the manual contour method was also significantly different from the standard contour method for rod trabecular number (rTb.N), rod trabecular thickness (rTb.Th), rod-rod and plate-rod junction densities (R-R Junc.D and P-R Junc.D) at the tibia. At the radius, the precision error was similar between the three different contour methods. Image quality was also found to significantly affect the ITS reproducibility. We concluded that ITS parameters are highly reproducible, giving assurance that future cross-sectional and longitudinal clinical HR-pQCT studies are feasible in the context of limited sample sizes.

Pulse joining cartridges

DOE Office of Scientific and Technical Information (OSTI.GOV)

Golovashchenko, Sergey Fedorovich; Bonnen, John Joseph Francis

A pulsed joining tool includes a tool body that defines a cavity that receives an inner tubular member and an outer tubular member and a pulse joining cartridge. The tubular members are nested together with the cartridge being disposed around the outer tubular member. The cartridge includes a conductor, such as a wire or foil, that extends around the outer tubular member and is insulated to separate a supply segment from a return segment. A source of stored electrical energy is discharged through the conductor to join the tubular members with an electromagnetic force pulse.

Pulse joining cartridges

DOEpatents

Golovashchenko, Sergey Fedorovich; Bonnen, John Joseph Francis

2016-08-23

A pulsed joining tool includes a tool body that defines a cavity that receives an inner tubular member and an outer tubular member and a pulse joining cartridge. The tubular members are nested together with the cartridge being disposed around the outer tubular member. The cartridge includes a conductor, such as a wire or foil, that extends around the outer tubular member and is insulated to separate a supply segment from a return segment. A source of stored electrical energy is discharged through the conductor to join the tubular members with an electromagnetic force pulse.

Coherent anti-stokes Raman scattering (CARS) microscopy: a novel technique for imaging the retina.

PubMed

Masihzadeh, Omid; Ammar, David A; Kahook, Malik Y; Lei, Tim C

2013-05-01

To image the cellular and noncellular structures of the retina in an intact mouse eye without the application of exogenous fluorescent labels using noninvasive, nondestructive techniques. Freshly enucleated mouse eyes were imaged using two nonlinear optical techniques: coherent anti-Stokes Raman scattering (CARS) and two-photon autofluorescence (TPAF). Cross sectional transverse sections and sequential flat (en face) sagittal sections were collected from a region of sclera approximately midway between the limbus and optic nerve. Imaging proceeded from the surface of the sclera to a depth of ∼60 μm. The fluorescent signal from collagen fibers within the sclera was evident in the TPAF channel; the scleral collagen fibers showed no organization and appeared randomly packed. The sclera contained regions lacking TPAF and CARS fluorescence of ∼3 to 15 μm in diameter that could represent small vessels or scleral fibroblasts. Intense punctate CARS signals from the retinal pigment epithelial layer were of a size and shape of retinyl storage esters. Rod outer segments could be identified by the CARS signal from their lipid-rich plasma membranes. CARS microscopy can be used to image the outer regions of the mammalian retina without the use of a fluorescent dye or exogenously expressed recombinant protein. With technical advancements, CARS/TPAF may represent a new avenue for noninvasively imaging the retina and might complement modalities currently used in clinical practice.

High levels of retinal membrane docosahexaenoic acid increase susceptibility to stress-induced degenerations⃞

PubMed Central

Tanito, Masaki; Brush, Richard S.; Elliott, Michael H.; Wicker, Lea D.; Henry, Kimberly R.; Anderson, Robert E.

2009-01-01

The fat-1 gene cloned from C. elegans encodes an n-3 fatty acid desaturase that converts n-6 to n-3 PUFA. Mice carrying the fat-1 transgene and wild-type controls were fed an n-3-deficient/n-6-enriched diet [fat-1- safflower oil (SFO) and wt-SFO, respectively]. Fatty acid profiles of rod outer segments (ROS), cerebellum, plasma, and liver demonstrated significantly lower n-6/n-3 ratios and higher docosahexaenoic acid (DHA) levels in fat-1-SFO compared with wt-SFO. When mice were exposed to light stress: 1) the outer nuclear layer (ONL) thickness was reduced; 2) amplitudes of the electroretinogram (ERG) were lower; 3) the number of apoptotic photoreceptor cells was greater; and 4) modification of retinal proteins by 4-hydroxyhexenal (4-HHE), an end-product of n-3 PUFA oxidation was increased in both fat-1-SFO and wt mice fed a regular lab chow diet compared with wt-SFO. The results indicate a positive correlation between the level of DHA, the degree of n-3 PUFA lipid peroxidation, and the vulnerability of the retina to photooxidative stress. In mice not exposed to intense light, the reduction in DHA resulted in reduced efficacy in phototransduction gain steps, while no differences in the retinal morphology or retinal biochemistry. These results highlight the dual roles of DHA in cellular physiology and pathology. PMID:19023138

77 FR 66580 - Notice of Availability of the Record of Decision (ROD) for the Gulf Coast Pipeline Project

Federal Register 2010, 2011, 2012, 2013, 2014

2012-11-06

... subordinate its rights, acquired under the Wetland Reserve Program, to allow the Gulf Coast Segment (Gulf.... Department of State (DOS) to build and operate the Keystone XL Project. In the original application, Trans... built in three segments: The approximately 850-mile long ``Steele City'' segment from the U.S. border to...

Study on a New Combination Method and High Efficiency Outer Rotor Type Permanent Magnet Motors

NASA Astrophysics Data System (ADS)

Enomoto, Yuji; Kitamura, Masashi; Motegi, Yasuaki; Andoh, Takashi; Ochiai, Makoto; Abukawa, Toshimi

The segment stator core, high space factor coil, and high efficiency magnet are indispensable technologies in the development of compact and a high efficiency motors. But adoption of the segment stator core and high space factor coil has not progressed in the field of outer rotor type motors, for the reason that the inner components cannot be laser welded together. Therefore, we have examined a segment stator core combination technology for the purposes of getting a large increase in efficiency and realizing miniaturization. We have also developed a characteristic estimation method which provides the most suitable performance for segment stator core motors.

Leaf seal for gas turbine stator shrouds and a nozzle band

DOEpatents

Burdgick, Steven Sebastian; Sexton, Brendan Francis

2002-01-01

A leaf seal assembly is secured to the trailing edge of a shroud segment for sealing between the shroud segment and the leading edge side wall of a nozzle outer band. The leaf seal includes a circumferentially elongated seal plate biased by a pair of spring clips disposed in a groove along the trailing edge of the shroud segment to maintain the seal plate in engagement with the flange on the leading edge side wall of the nozzle outer band. The leaf seal plate and spring clips receive pins tack-welded to the shroud segment to secure the leaf seal assembly in place.

Structural and functional changes associated with normal and abnormal fundus autofluorescence in patients with retinitis pigmentosa.

PubMed

Greenstein, Vivienne C; Duncker, Tobias; Holopigian, Karen; Carr, Ronald E; Greenberg, Jonathan P; Tsang, Stephen H; Hood, Donald C

2012-02-01

To analyze the structure and visual function of regions bordering the hyperautofluorescent ring/arcs in retinitis pigmentosa. Twenty-one retinitis pigmentosa patients (21 eyes) with rings/arcs and 21 normal individuals (21 eyes) were studied. Visual sensitivity in the central 10° was measured with microperimetry. Retinal structure was evaluated with spectral-domain optical coherence tomography. The distance from the fovea to disruption/loss of the inner outer segment (IS/OS) junction and thicknesses of the total receptor plus retinal pigment epithelial complex and outer segment plus retinal pigment epithelial complex layers were measured. Results were compared with measurements of the distance from the fovea to the inner and outer borders of the ring/arc seen on fundus autofluorescence. Disruption/loss of the inner outer segment junction occurred closer to the inner border of the ring/arc and it was closer to the fovea in eight eyes. For 19 eyes, outer segment plus and receptor plus RPE complex thicknesses were significantly decreased at locations closer to the fovea than the appearance of the inner border of hyperautofluorescence. Mean visual sensitivity was decreased inside, across, and outside the ring/arc by 3.5 ± 3.8, 8.9 ± 4.8, and 17.0 ± 2.4 dB, respectively. Structural and functional changes can occur inside the hyperfluorescent ring/arc in retinitis pigmentosa.

The Properties of Outer Retinal Band Three Investigated With Adaptive-Optics Optical Coherence Tomography.

PubMed

Jonnal, Ravi S; Gorczynska, Iwona; Migacz, Justin V; Azimipour, Mehdi; Zawadzki, Robert J; Werner, John S

2017-09-01

Optical coherence tomography's (OCT) third outer retinal band has been attributed to the zone of interdigitation between RPE cells and cone outer segments. The purpose of this paper is to investigate the structure of this band with adaptive optics (AO)-OCT. Using AO-OCT, images were obtained from two subjects. Axial structure was characterized by measuring band 3 thickness and separation between bands 2 and 3 in segmented cones. Lateral structure was characterized by correlation of band 3 with band 2 and comparison of their power spectra. Band thickness and separation were also measured in a clinical OCT image of one subject. Band 3 thickness ranged from 4.3 to 6.4 μm. Band 2 correlations ranged between 0.35 and 0.41 and power spectra of both bands confirmed peak frequencies that agree with histologic density measurements. In clinical images, band 3 thickness was between 14 and 19 μm. Measurements of AO-OCT of interband distance were lower than our corresponding clinical OCT measurements. Band 3 originates from a structure with axial extent similar to a single surface. Correlation with band 2 suggests an origin within the cone photoreceptor. These two observations indicate that band 3 corresponds predominantly to cone outer segment tips (COST). Conventional OCT may overestimate both the thickness of band 3 and outer segment length.

The Properties of Outer Retinal Band Three Investigated With Adaptive-Optics Optical Coherence Tomography

PubMed Central

Jonnal, Ravi S.; Gorczynska, Iwona; Migacz, Justin V.; Azimipour, Mehdi; Zawadzki, Robert J.; Werner, John S.

2017-01-01

Purpose Optical coherence tomography's (OCT) third outer retinal band has been attributed to the zone of interdigitation between RPE cells and cone outer segments. The purpose of this paper is to investigate the structure of this band with adaptive optics (AO)-OCT. Methods Using AO-OCT, images were obtained from two subjects. Axial structure was characterized by measuring band 3 thickness and separation between bands 2 and 3 in segmented cones. Lateral structure was characterized by correlation of band 3 with band 2 and comparison of their power spectra. Band thickness and separation were also measured in a clinical OCT image of one subject. Results Band 3 thickness ranged from 4.3 to 6.4 μm. Band 2 correlations ranged between 0.35 and 0.41 and power spectra of both bands confirmed peak frequencies that agree with histologic density measurements. In clinical images, band 3 thickness was between 14 and 19 μm. Measurements of AO-OCT of interband distance were lower than our corresponding clinical OCT measurements. Conclusions Band 3 originates from a structure with axial extent similar to a single surface. Correlation with band 2 suggests an origin within the cone photoreceptor. These two observations indicate that band 3 corresponds predominantly to cone outer segment tips (COST). Conventional OCT may overestimate both the thickness of band 3 and outer segment length. PMID:28877320

Anatomical correlates to the bands seen in the outer retina by optical coherence tomography: literature review and model.

PubMed

Spaide, Richard F; Curcio, Christine A

2011-09-01

To evaluate the validity of commonly used anatomical designations for the four hyperreflective outer retinal bands seen in current-generation optical coherence tomography, a scale model of outer retinal morphology was created using published information for direct comparison with optical coherence tomography scans. Articles and books concerning histology of the outer retina from 1900 until 2009 were evaluated, and data were used to create a scale model drawing. Boundaries between outer retinal tissue compartments described by the model were compared with intensity variations of representative spectral-domain optical coherence tomography scans using longitudinal reflectance profiles to determine the region of origin of the hyperreflective outer retinal bands. This analysis showed a high likelihood that the spectral-domain optical coherence tomography bands attributed to the external limiting membrane (the first, innermost band) and to the retinal pigment epithelium (the fourth, outermost band) are correctly attributed. Comparative analysis showed that the second band, often attributed to the boundary between inner and outer segments of the photoreceptors, actually aligns with the ellipsoid portion of the inner segments. The third band corresponded to an ensheathment of the cone outer segments by apical processes of the retinal pigment epithelium in a structure known as the contact cylinder. Anatomical attributions and subsequent pathophysiologic assessments pertaining to the second and third outer retinal hyperreflective bands may not be correct. This analysis has identified testable hypotheses for the actual correlates of the second and third bands. Nonretinal pigment epithelium contributions to the fourth band (e.g., Bruch membrane) remain to be determined.

Early simultaneous fundus autofluorescence and optical coherence tomography features after pars plana vitrectomy for primary rhegmatogenous retinal detachment.

PubMed

Dell'Omo, Roberto; Mura, Marco; Lesnik Oberstein, Sarit Y; Bijl, Heico; Tan, H Stevie

2012-04-01

To describe fundus autofluorescence and optical coherence tomography (OCT) features of the macula after pars plana vitrectomy for rhegmatogenous retinal detachment. Thirty-three eyes of 33 consecutive patients with repaired rhegmatogenous retinal detachment with or without the involvement of the macula were prospectively investigated with simultaneous fundus autofluorescence and OCT imaging using the Spectralis HRA+OCT (Heidelberg Engineering, Heidelberg, Germany) within a few weeks after the operation. Fundus autofluorescence imaging of the macula showed lines of increased and decreased autofluorescence in 19 cases (57.6%). On OCT, these lines corresponded to the following abnormalities: outer retinal folds, inner retinal folds, and skip reflectivity abnormalities of the photoreceptor inner segment/outer segment band. Other OCT findings, not related to abnormal lines on fundus autofluorescence, consisted of disruption of photoreceptor inner segment/outer segment band and collection of intraretinal or subretinal fluid. The presence of outer retinal folds significantly related to metamorphopsia but did not relate to poor postoperative visual acuity. Partial-thickness retinal folds occur commonly after vitrectomy for rhegmatogenous retinal detachment repair and may represent an important anatomical substrate for postoperative metamorphopsia. Fundus autofluorescence and OCT are both sensitive techniques for the detection of these abnormalities.

DYF-1 Is Required for Assembly of the Axoneme in Tetrahymena thermophila▿ †

PubMed Central

Dave, Drashti; Wloga, Dorota; Sharma, Neeraj; Gaertig, Jacek

2009-01-01

In most cilia, the axoneme can be subdivided into three segments: proximal (the transition zone), middle (with outer doublet microtubules), and distal (with singlet extensions of outer doublet microtubules). How the functionally distinct segments of the axoneme are assembled and maintained is not well understood. DYF-1 is a highly conserved ciliary protein containing tetratricopeptide repeats. In Caenorhabditis elegans, DYF-1 is specifically needed for assembly of the distal segment (G. Ou, O. E. Blacque, J. J. Snow, M. R. Leroux, and J. M. Scholey. Nature. 436:583-587, 2005). We show that Tetrahymena cells lacking an ortholog of DYF-1, Dyf1p, can assemble only extremely short axoneme remnants that have structural defects of diverse natures, including the absence of central pair and outer doublet microtubules and incomplete or absent B tubules on the outer microtubules. Thus, in Tetrahymena, DYF-1 is needed for either assembly or stability of the entire axoneme. Our observations support the conserved function for DYF-1 in axoneme assembly or stability but also show that the consequences of loss of DYF-1 for axoneme segments are organism specific. PMID:19581442

Turbine stator vane segment having internal cooling circuits

DOEpatents

Jones, Raymond Joseph; Burns, James Lee; Bojappa, Parvangada Ganapathy; Jones, Schotsch Margaret

2003-01-01

A turbine stator vane includes outer and inner walls each having outer and inner chambers and a vane extending between the outer and inner walls. The vane includes first, second, third, fourth and fifth cavities for flowing a cooling medium. The cooling medium enters the outer chamber of the outer wall, flows through an impingement plate for impingement cooling of the outer band wall defining in part the hot gas path and through openings in the first, second and fourth cavities for flow radially inwardly, cooling the vane. The spent cooling medium flows into the inner wall and inner chamber for flow through an impingement plate radially outwardly to cool the inner wall. The spent cooling medium flows through the third cavity for egress from the turbine vane segment from the outer wall. The first, second or third cavities contain inserts having impingement openings for impingement cooling of the vane walls. The fifth cavity provides air cooling for the trailing edge.

Gas turbine row #1 steam cooled vane

DOEpatents

Cunha, Frank J.

2000-01-01

A design for a vane segment having a closed-loop steam cooling system is provided. The vane segment comprises an outer shroud, an inner shroud and an airfoil, each component having a target surface on the inside surface of its walls. A plurality of rectangular waffle structures are provided on the target surface to enhance heat transfer between each component and cooling steam. Channel systems are provided in the shrouds to improve the flow of steam through the shrouds. Insert legs located in cavities in the airfoil are also provided. Each insert leg comprises outer channels located on a perimeter of the leg, each outer channel having an outer wall and impingement holes on the outer wall for producing impingement jets of cooling steam to contact the airfoil's target surface. Each insert leg further comprises a plurality of substantially rectangular-shaped ribs located on the outer wall and a plurality of openings located between outer channels of the leg to minimize cross flow degradation.

Morphological changes in the anterior segment of the Abyssinian cat eye with hereditary rod-cone degeneration.

PubMed

May, Chr Albrecht; Lütjen-Drecoll, Elke; Narfström, Kristina

2005-10-01

The purpose of this study was to investigate morphological changes of the anterior segment of the eye in Abyssinian cats with progressive rod-cone degeneration and to correlate them with blood flow data obtained in the same animals. Sections of the left eyes of six normal cats and of eight cats with different stages of hereditary retinal degeneration were prepared for transmission and scanning electron microscopy. Tangential and sagittal sections were also stained with antibodies against substance P, tyrosine hydroxylase, panneuronal marker PGP9.5, nitric oxide synthase, synaptophysin, and smooth muscle alpha-actin. In Abyssinian cats with hereditary rod-cone degeneration, significant changes were observed in the iris consisting of irregularities in the vascular wall of smaller arteries without changes in their innervation pattern. The ciliary processes were shorter than in normal cats, and their structure appeared more compact and retracted. Slight changes were also observed in the anterior part of the ciliary epithelium. The anterior chamber angle region did not appear to be affected. Clear morphological correlations to the physiological blood flow data were observed in the anterior eye segment, pointing not only to functional but also morphological vascular abnormalities in this animal model for retinitis pigmentosa.

Reflectance Spectra of Peacock Feathers and the Turning Angles of Melanin Rods in Barbules.

PubMed

Okazaki, Toshio

2018-02-01

I analyzed the association between the reflectance spectra and melanin rod arrangement in barbules of the eyespot of peacock feathers. The reflectance spectra from the yellow-green feather of the eyespot indicated double peaks of 430 and 540 nm. The maximum reflectance spectrum of the blue feather was 480 nm, and that of the dark blue feather was 420 nm. The reflectance spectra from brown feathers indicated double peaks of 490 and 610 nm. Transmission electron microscopic analysis confirmed that melanin rods were arranged fanwise in the outer layer toward the barbule tips. In addition, using polarized light microscope, I attempted to determine whether the turning angles of melanin rods in the barbules reflected different colors. The turning angle of the polarizing axis of the barbules was supported by that of the melanin rods, observed using transmission electron microscopic images. To compare the turning angle of melanin rods in the respective barbules, I calculated the opening width of the fanwise melanin rods by dividing the width of the barbules by the turning angle of the polarizing axis of barbules and obtained a positive correlation between the reflectance spectra and opening width of the fanwise melanin rods. Moreover, the widely spreading reflection from the barbules may occur because of the fanwise melanin rod arrangement.

Lathe Attachment Finishes Inner Surface of Tubes

NASA Technical Reports Server (NTRS)

Lancki, A. J.

1982-01-01

Extremely smooth finishes are machined on inside surfaces of tubes by new attachment for a lathe. The relatively inexpensive accessory, called a "microhone," holds a honing stone against workpiece by rigid tangs instead of springs as in conventional honing tools. Inner rod permits adjustment of microhoning stone, while outer tube supports assembly. Outer tube is held between split blocks on lathe toolpost. Microhoning can be done with either microhone or workpiece moving and other member stationary.

Differences in Trabecular Microstructure Between Black and White Women Assessed by Individual Trabecular Segmentation Analysis of HR-pQCT Images

PubMed Central

Putman, Melissa S; Yu, Elaine W; Lin, David; Darakananda, Karin; Finkelstein, Joel S; Bouxsein, Mary L

2017-01-01

Black women have lower fracture risk compared with white women, which may be partly explained by improved volumetric bone mineral density (vBMD) and bone microarchitecture primarily within the cortical bone compartment. To determine if there are differences in trabecular microstructure, connectivity, and alignment according to race/ethnicity, we performed individual trabecular segmentation (ITS) analyses on high-resolution peripheral quantitative computed tomography (HR-pQCT) scans of the distal radius and tibia in 273 peri- and postmenopausal black (n = 100) and white (n = 173) women participating in the Study of Women’s Health Across the Nation in Boston. Unadjusted analyses showed that black women had greater trabecular plate volume fraction, plate thickness, plate number density, and plate surface area along with greater axial alignment of trabeculae, whereas white women had greater trabecular rod tissue fraction (p < 0.05 for all). Adjustment for clinical covariates augmented these race/ethnicity-related differences in plates and rods, such that white women had greater trabecular rod number density and rod-rod connectivity, whereas black women continued to have superior plate structural characteristics and axial alignment (p < 0.05 for all). These differences remained significant after adjustment for hip BMD and trabecular vBMD. In conclusion, black women had more plate-like trabecular morphology and higher axial alignment of trabeculae, whereas white women had more rod-like trabeculae. These differences may contribute to the improved bone strength and lower fracture risk observed in black women. PMID:27958659

The COSIMA experiments and their verification, a data base for the validation of two phase flow computer codes

NASA Astrophysics Data System (ADS)

Class, G.; Meyder, R.; Stratmanns, E.

1985-12-01

The large data base for validation and development of computer codes for two-phase flow, generated at the COSIMA facility, is reviewed. The aim of COSIMA is to simulate the hydraulic, thermal, and mechanical conditions in the subchannel and the cladding of fuel rods in pressurized water reactors during the blowout phase of a loss of coolant accident. In terms of fuel rod behavior, it is found that during blowout under realistic conditions only small strains are reached. For cladding rupture extremely high rod internal pressures are necessary. The behavior of fuel rod simulators and the effect of thermocouples attached to the cladding outer surface are clarified. Calculations performed with the codes RELAP and DRUFAN show satisfactory agreement with experiments. This can be improved by updating the phase separation models in the codes.

Flexible growing rods: a pilot study to determine if polymer rod constructs may provide stability to skeletally immature spines

PubMed Central

2015-01-01

Background Surgical treatments for early onset scoliosis (EOS), including growing rod constructs, involve many complications. Some are due to biomechanical factors. A construct that is more flexible than current instrumentation systems may reduce complications. The purpose of this preliminary study was to determine spine range of motion (ROM) after implantation of simulated growing rod constructs with a range of clinically relevant structural properties. The hypothesis was that ROM of spines instrumented with polyetheretherketone (PEEK) rods would be greater than metal rods and lower than noninstrumented controls. Further, adjacent segment motion was expected to be lower with polymer rods compared to conventional systems. Methods Biomechanical tests were conducted on 6 skeletally immature porcine thoracic spines (domestic swine, 35-40 kg). Spines were harvested after death from swine that had been utilized for other studies (IACUC approved) which had not involved the spine. Paired pedicle screws were used as anchors at proximal and distal levels. Specimens were tested under the following conditions: control, then dual rods of PEEK (6.25 mm), titanium (4 mm), and CoCr (5 mm) alloy. Lateral bending (LB) and flexion-extension (FE) moments of ±5 Nm were applied. Vertebral rotations were measured using video. Differences were determined by two-tailed t-tests and Bonferroni correction with four primary comparisons: PEEK vs control and PEEK vs CoCr, in LB and FE (α=0.05/4). Results In LB, ROM of specimens with PEEK rods was lower than control at each instrumented level. ROM was greater for PEEK rods than both Ti and CoCr at every instrumented level. Mean ROM at proximal and distal noninstrumented levels was lower for PEEK than for Ti and CoCr. In FE, mean ROM at proximal and distal noninstrumented levels was lower for PEEK than for metal. Combining treated levels, in LB, ROM for PEEK rods was 35% of control (p<0.0001) and 270% of CoCr rods (p<0.01). In FE, ROM with PEEK was 27% of control (p<0.001) and 180% of CoCr (p<0.01). Conclusions PEEK rods decreased flexibility versus noninstumented controls, and increased flexibility versus metal rods. Smaller increases in ROM at proximal and distal adjacent motion segments occurred with PEEK compared to metal rods, which may help decrease junctional kyphosis. Flexible growing rods may eventually help improve treatment options for young patients with severe deformity. PMID:25810752

The permeability of the cGMP-activated channel to organic cations in retinal rods of the tiger salamander.

PubMed Central

Picco, C; Menini, A

1993-01-01

1. The permeability of the channel activated by guanosine 3',5'-cyclic monophosphate (cGMP) to many organic monovalent cations was determined by recording macroscopic currents in excised inside-out patches of plasma membrane from isolated retinal rod outer segments of the tiger salamander. 2. Current-voltage relations were measured when the NaCl of the bathing medium was replaced by salts of organic cations. Permeability ratios relative to Na+ ions were calculated with the Goldman-Hodgkin-Katz potential equation from the measured changes of reversal potentials. 3. Hydroxylammonium+, hydrazinium+ and methylammonium+, which are molecules of very similar shape and size, permeate the channel with very different permeability ratios: 5.92, 1.99 and 0.60 respectively. 4. Methylated and ethylated ammonium+ compounds were investigated. It was found that, not only methylammonium+, but also dimethylammonium+ and ethylammonium+ were permeant with permeability ratios of 0.6, 0.14 and 0.16 respectively. Trimethylammonium+, tetramethylammonium+, diethylammonium+, triethylammonium+, and tetraethylammonium+ were not permeant. 5. Guanidinium+ and its derivatives formamidinium+, aminoguanidinium+, acetamidinium+ and methylguanidinium+ were all permeant with permeability ratios 1.12, 1.00, 0.63, 0.36 and 0.33 respectively. 6. The cGMP-activated channel was found to be permeable to at least thirteen organic cations. Molecular models of the permeant cations indicate that the cross-section of the narrowest part of the pore must be at least as large as a rectangle of 0.38 x 0.5 nm dimensions. PMID:7683718

Dual load path ball screw with rod end swivel

NASA Technical Reports Server (NTRS)

Wngett, Paul (Inventor)

2002-01-01

A dual drive ball has a ball screw shaft coupled at one end to a gear train and coupled at the other end to a ball screw nut. The ball screw shaft and ball screw nut are connected through complementary helical grooves filled with ball bearing balls. The outer surface of the ball screw nut is plined and can be driven by a second gear train. An output tube is coupled at one end to the ball screw nut and at its opposite end has a connector portion with a groove on its inner surface. A rod end has a coupling member for coupling to a surface to be actuated and a shaft portion with a groobe on its outer surface. This shaft portion is received with in the outputtube portion and the corresponding grooves are coupled through the use of a plurality of ball bearing balls.

Measuring In Vivo Free Radical Production by the Outer Retina

PubMed Central

Berkowitz, Bruce A.; Bredell, Bryce X.; Davis, Christopher; Samardzija, Marijana; Grimm, Christian; Roberts, Robin

2015-01-01

Purpose Excessive and continuously produced free radicals in the outer retina are implicated in retinal aging and the pathogenesis of sight-threatening retinopathies, yet measuring outer retinal oxidative stress in vivo remains a challenge. Here, we test the hypothesis that continuously produced paramagnetic free radicals from the outer retina can be measured in vivo using high-resolution (22-μm axial resolution) 1/T1magnetic resonance imaging (MRI) without and with a confirmatory quench (quench-assisted MRI). Methods Low-dose sodium iodate–treated and diabetic C57Bl6/J mice (and their controls), and rod-dominated (129S6) or cone-only R91W;Nrl−/− mice were studied. In dark-adapted groups, 1/T1 was mapped transretinally in vivo without or with (1) the antioxidant combination of methylene blue (MB) and α-lipoic acid (LPA), or (2) light exposure; in subgroups, retinal superoxide production was measured ex vivo (lucigenin). Results In the sodium iodate model, retinal superoxide production and outer retina-specific 1/T1 values were both significantly greater than normal and corrected to baseline with MB+LPA therapy. Nondiabetic mice at two ages and 1.2-month diabetic mice (before the appearance of oxidative stress) had similar transretinal 1/T1 profiles. By 2.3 months of diabetes, only outer retinal 1/T1 values were significantly greater than normal and were corrected to baseline with MB+LPA therapy. In mice with healthy photoreceptors, a light quench caused 1/T1 of rods, but not cones, to significantly decrease from their values in the dark. Conclusions Quench-assisted MRI is a feasible method for noninvasively measuring normal and pathologic production of free radicals in photoreceptors/RPE in vivo. PMID:26670830

Rescue of compromised lysosomes enhances degradation of photoreceptor outer segments and reduces lipofuscin-like autofluorescence in retinal pigmented epithelial cells.

PubMed

Guha, Sonia; Liu, Ji; Baltazar, Gabe; Laties, Alan M; Mitchell, Claire H

2014-01-01

Healthful cell maintenance requires the efficient degradative processing and removal of waste material. Retinal pigmented epithelial (RPE) cells have the onerous task of degrading both internal cellular debris generated through autophagy as well as phagocytosed photoreceptor outer segments. We propose that the inadequate processing material with the resulting accumulation of cellular waste contributes to the downstream pathologies characterized as age-related macular degeneration (AMD). The lysosomal enzymes responsible for clearance function optimally over a narrow range of acidic pH values; elevation of lysosomal pH by compounds like chloroquine or A2E can impair degradative enzyme activity and lead to a lipofuscin-like autofluorescence. Restoring acidity to the lysosomes of RPE cells can enhance activity of multiple degradative enzymes and is therefore a logical target in early AMD. We have identified several approaches to reacidify lysosomes of compromised RPE cells; stimulation of beta-adrenergic, A2A adenosine and D5 dopamine receptors each lowers lysosomal pH and improves degradation of outer segments. Activation of the CFTR chloride channel also reacidifies lysosomes and increases degradation. These approaches also restore the lysosomal pH of RPE cells from aged ABCA4(-/-) mice with chronically high levels of A2E, suggesting that functional signaling pathways to reacidify lysosomes are retained in aged cells like those in patients with AMD. Acidic nanoparticles transported to RPE lysosomes also lower pH and improve degradation of outer segments. In summary, the ability of diverse approaches to lower lysosomal pH and enhance outer segment degradation support the proposal that lysosomal acidification can prevent the accumulation of lipofuscin-like material in RPE cells.

Fasudil, a Clinically Used ROCK Inhibitor, Stabilizes Rod Photoreceptor Synapses after Retinal Detachment.

PubMed

Townes-Anderson, Ellen; Wang, Jianfeng; Halász, Éva; Sugino, Ilene; Pitler, Amy; Whitehead, Ian; Zarbin, Marco

2017-06-01

Retinal detachment disrupts the rod-bipolar synapse in the outer plexiform layer by retraction of rod axons. We showed that breakage is due to RhoA activation whereas inhibition of Rho kinase (ROCK), using Y27632, reduces synaptic damage. We test whether the ROCK inhibitor fasudil, used for other clinical applications, can prevent synaptic injury after detachment. Detachments were made in pigs by subretinal injection of balanced salt solution (BSS) or fasudil (1, 10 mM). In some animals, fasudil was injected intravitreally after BSS-induced detachment. After 2 to 4 hours, retinae were fixed for immunocytochemistry and confocal microscopy. Axon retraction was quantified by imaging synaptic vesicle label in the outer nuclear layer. Apoptosis was analyzed using propidium iodide staining. For biochemical analysis by Western blotting, retinal explants, detached from retinal pigmented epithelium, were cultured for 2 hours. Subretinal injection of fasudil (10 mM) reduced retraction of rod spherules by 51.3% compared to control detachments ( n = 3 pigs, P = 0.002). Intravitreal injection of 10 mM fasudil, a more clinically feasible route of administration, also reduced retraction (28.7%, n = 5, P < 0.05). Controls had no photoreceptor degeneration at 2 hours, but by 4 hours apoptosis was evident. Fasudil 10 mM reduced pyknotic nuclei by 55.7% ( n = 4, P < 0.001). Phosphorylation of cofilin and myosin light chain, downstream effectors of ROCK, was decreased with 30 μM fasudil ( n = 8-10 explants, P < 0.05). Inhibition of ROCK signaling with fasudil reduced photoreceptor degeneration and preserved the rod-bipolar synapse after retinal detachment. These results support the possibility, previously tested with Y27632, that ROCK inhibition may attenuate synaptic damage in iatrogenic detachments.

Joint segmentation of lumen and outer wall from femoral artery MR images: Towards 3D imaging measurements of peripheral arterial disease.

PubMed

Ukwatta, Eranga; Yuan, Jing; Qiu, Wu; Rajchl, Martin; Chiu, Bernard; Fenster, Aaron

2015-12-01

Three-dimensional (3D) measurements of peripheral arterial disease (PAD) plaque burden extracted from fast black-blood magnetic resonance (MR) images have shown to be more predictive of clinical outcomes than PAD stenosis measurements. To this end, accurate segmentation of the femoral artery lumen and outer wall is required for generating volumetric measurements of PAD plaque burden. Here, we propose a semi-automated algorithm to jointly segment the femoral artery lumen and outer wall surfaces from 3D black-blood MR images, which are reoriented and reconstructed along the medial axis of the femoral artery to obtain improved spatial coherence between slices of the long, thin femoral artery and to reduce computation time. The developed segmentation algorithm enforces two priors in a global optimization manner: the spatial consistency between the adjacent 2D slices and the anatomical region order between the femoral artery lumen and outer wall surfaces. The formulated combinatorial optimization problem for segmentation is solved globally and exactly by means of convex relaxation using a coupled continuous max-flow (CCMF) model, which is a dual formulation to the convex relaxed optimization problem. In addition, the CCMF model directly derives an efficient duality-based algorithm based on the modern multiplier augmented optimization scheme, which has been implemented on a GPU for fast computation. The computed segmentations from the developed algorithm were compared to manual delineations from experts using 20 black-blood MR images. The developed algorithm yielded both high accuracy (Dice similarity coefficients ≥ 87% for both the lumen and outer wall surfaces) and high reproducibility (intra-class correlation coefficient of 0.95 for generating vessel wall area), while outperforming the state-of-the-art method in terms of computational time by a factor of ≈ 20. Copyright © 2015 Elsevier B.V. All rights reserved.

The biomechanical consequences of rod reduction on pedicle screws: should it be avoided?

PubMed

Paik, Haines; Kang, Daniel G; Lehman, Ronald A; Gaume, Rachel E; Ambati, Divya V; Dmitriev, Anton E

2013-11-01

Rod contouring is frequently required to allow for appropriate alignment of pedicle screw-rod constructs. When residual mismatch is still present, a rod persuasion device is often used to achieve further rod reduction. Despite its popularity and widespread use, the biomechanical consequences of this technique have not been evaluated. To evaluate the biomechanical fixation strength of pedicle screws after attempted reduction of a rod-pedicle screw mismatch using a rod persuasion device. Fifteen 3-level, human cadaveric thoracic specimens were prepared and scanned for bone mineral density. Osteoporotic (n=6) and normal (n=9) specimens were instrumented with 5.0-mm-diameter pedicle screws; for each pair of comparison level tested, the bilateral screws were equal in length, and the screw length was determined by the thoracic level and size of the vertebra (35 to 45 mm). Titanium 5.5-mm rods were contoured and secured to the pedicle screws at the proximal and distal levels. For the middle segment, the rod on the right side was intentionally contoured to create a 5-mm residual gap between the inner bushing of the pedicle screw and the rod. A rod persuasion device was then used to engage the setscrew. The left side served as a control with perfect screw/rod alignment. After 30 minutes, constructs were disassembled and vertebrae individually potted. The implants were pulled in-line with the screw axis with peak pullout strength (POS) measured in Newton (N). For the proximal and distal segments, pedicle screws on the right side were taken out and reinserted through the same trajectory to simulate screw depth adjustment as an alternative to rod reduction. Pedicle screws reduced to the rod generated a 48% lower mean POS (495±379 N) relative to the controls (954±237 N) (p<.05) and significantly decreased work energy to failure (p<.05). Nearly half (n=7) of the pedicle screws had failed during the reduction attempt with visible pullout of the screw. After reduction, decreased POS was observed in both normal (p<.05) and osteoporotic (p<.05) bone. Back out and reinsertion of the screw resulted in no significant difference in mean POS, stiffness, and work energy to failure (p>.05). In circumstances where a rod is not fully seated within the pedicle screw, the use of a rod persuasion device decreases the overall POS and work energy to failure of the screw or results in outright failure. Further rod contouring or correction of pedicle screw depth of insertion may be warranted to allow for appropriate alignment of the longitudinal rods. Published by Elsevier Inc.

High-voltage testing of a 500-kV dc photocathode electron gun.

PubMed

Nagai, Ryoji; Hajima, Ryoichi; Nishimori, Nobuyuki; Muto, Toshiya; Yamamoto, Masahiro; Honda, Yosuke; Miyajima, Tsukasa; Iijima, Hokuto; Kuriki, Masao; Kuwahara, Makoto; Okumi, Shoji; Nakanishi, Tsutomu

2010-03-01

A high-voltage dc photocathode electron gun was successfully conditioned up to a voltage of 550 kV and a long-time holding test for 8 h was demonstrated at an acceleration voltage of 500 kV. The dc photocathode electron gun is designed for future light sources based on energy-recovery linac and consists of a Cockcroft-Walton generator, a segmented cylindrical ceramic insulator, guard-ring electrodes, a support-rod electrode, a vacuum chamber, and a pressurized insulating gas tank. The segmented cylindrical ceramic insulator and the guard-ring electrodes were utilized to prevent any damage to the insulator from electrons emitted by the support-rod electrode.

Comparison between Measured and Simulated Radiation Doses in the Matoroshka-R Spherical phantom Experiment#1 and Area Monitoring aboard International Space Station using PADLES from May - Sep. 2012

NASA Astrophysics Data System (ADS)

Nagamatsu, Aiko; Tolochek, Raisa; Shurshakov, Vyacheslav; Nikolaev, Igor; Tawara, Hiroko; Kitajo, Keiichi; Shimada, Ken

The measurement of radiation environmental parameters in space is essential to support radiation risk assessments for astronauts and establish a benchmark for space radiation models for present and future human space activities. Since Japanese Experiment Module ‘KIBO’ was attached to the International Space Station (ISS) in 2008, we have been performing continuous space radiation dosimetery using a PADLES (Passive Dosimeter for Life-Science Experiments in Space) consisting of CR-39 PNTDs (Plastic Nuclear track detectors) and TLD-MSOs (Mg2SiO4:Tb) for various space experiments onboard the ‘KIBO’ part of the ISS. The MATROSHKA-R experiments aims to verify of dose distributions in a human body during space flight. The phantom consists of tissue equivalent material covered by a poncho jacket with 32 pockets on the surface. 20 container rods with dosimeters can be struck into the spherical phantom. Its diameter is 370 mm and it is 32 kg in weight. The first experiment onboard the KIBO at Forward No.2 area (JPM1F2 Rack2) was conducted over 114 days from 21 May to 12 September 2012 (the installation schedule inside the phantom) on the way to solar cycle 24th upward curve. 16 PADLES packages were deployed into 16 poncho pockets on the surface of the spherical phantom. Another 12 PADLES packages were deployed inside 4 rods (3 packages per rod in the outer, middle and inner side). Area monitoring in the KIBO was conducted in the same period (Area PADLES series #8 from 15 May to 16 September, 2012). Absorbed doses were measured at 17 area monitoring points in the KIBO and 28 locations (16 packages in poncho pockets and 12 inside 4 rods) in the phantom. The maximum value measured with the PADLES in the poncho pockets on the surface of the spherical phantom facing the outer wall was 0.43 mGy/day and the minimum value measured with the PADLES in the poncho pockets on the surface of the spherical phantom facing the KIBO interior was 0.30 mGy/day. The maximum absorbed doses measured inside rods was 0.28 mGy/day and the minimum value was 0.19 mGy/day. This indicates doses measured from the dosimeters placed in the outer side of each rod are relatively high compared to the doses placed in the center of rod. At this time, we also would like to show the preliminary results of comparative study between measured and Simulated Radiation Doses using the Particle and Heavy Ion Transport code System (PHITS) calculations with well developed shielding model of the KIBO and numerical spherical phantom inside.

Activation and quenching of the phototransduction cascade in retinal cones as inferred from electrophysiology and mathematical modeling

PubMed Central

Astakhova, Luba; Firsov, Michael

2015-01-01

Purpose To experimentally identify and quantify factors responsible for the lower sensitivity of retinal cones compared to rods. Methods Electrical responses of frog rods and fish (Carassius) cones to short flashes of light were recorded using the suction pipette technique. A fast solution changer was used to apply a solution that fixed intracellular Ca2+ concentration at the prestimulus level, thereby disabling Ca2+ feedback, to the outer segment (OS). The results were analyzed with a specially designed mathematical model of phototransduction. The model included all basic processes of activation and quenching of the phototransduction cascade but omitted unnecessary mechanistic details of each step. Results Judging from the response versus intensity curves, Carassius cones were two to three orders of magnitude less sensitive than frog rods. There was a large scatter in sensitivity among individual cones, with red-sensitive cones being on average approximately two times less sensitive than green-sensitive ones. The scatter was mostly due to different signal amplification, since the kinetic parameters of the responses among cones were far less variable than sensitivity. We argue that the generally accepted definition of the biochemical amplification in phototransduction cannot be used for comparing amplification in rods and cones, since it depends on an irrelevant factor, that is, the cell’s volume. We also show that the routinely used simplified parabolic curve fitting to an initial phase of the response leads to a few-fold underestimate of the amplification. We suggest a new definition of the amplification that only includes molecular parameters of the cascade activation, and show how it can be derived from experimental data. We found that the mathematical model with unrestrained parameters can yield an excellent fit to experimental responses. However, the fits with wildly different sets of parameters can be virtually indistinguishable, and therefore cannot provide meaningful data on underlying mechanisms. Based on results of Ca2+-clamp experiments, we developed an approach to strongly constrain the values of many key parameters that set the time course and sensitivity of the photoresponse (such as the dark turnover rate of cGMP, rates of turnoffs of the photoactivated visual pigment and phosphodiesterase, and kinetics of Ca2+ feedback). We show that applying these constraints to our mathematical model enables accurate determination of the biochemical amplification in phototransduction. It appeared that, contrary to many suggestions, maximum biochemical amplification derived for “best” Carassius cones was as high as in frog rods. On the other hand, all turnoff and recovery reactions in cones proceeded approximately 10 times faster than in rods. Conclusions The main cause of the differing sensitivity of rods and cones is cones’ ability to terminate their photoresponse faster. PMID:25866462

Partially segmented deformable mirror

DOEpatents

Bliss, E.S.; Smith, J.R.; Salmon, J.T.; Monjes, J.A.

1991-05-21

A partially segmented deformable mirror is formed with a mirror plate having a smooth and continuous front surface and a plurality of actuators to its back surface. The back surface is divided into triangular areas which are mutually separated by grooves. The grooves are deep enough to make the plate deformable and the actuators for displacing the mirror plate in the direction normal to its surface are inserted in the grooves at the vertices of the triangular areas. Each actuator includes a transducer supported by a receptacle with outer shells having outer surfaces. The vertices have inner walls which are approximately perpendicular to the mirror surface and make planar contacts with the outer surfaces of the outer shells. The adhesive which is used on these contact surfaces tends to contract when it dries but the outer shells can bend and serve to minimize the tendency of the mirror to warp. 5 figures.

Partially segmented deformable mirror

DOEpatents

Bliss, Erlan S.; Smith, James R.; Salmon, J. Thaddeus; Monjes, Julio A.

1991-01-01

A partially segmented deformable mirror is formed with a mirror plate having a smooth and continuous front surface and a plurality of actuators to its back surface. The back surface is divided into triangular areas which are mutually separated by grooves. The grooves are deep enough to make the plate deformable and the actuators for displacing the mirror plate in the direction normal to its surface are inserted in the grooves at the vertices of the triangular areas. Each actuator includes a transducer supported by a receptacle with outer shells having outer surfaces. The vertices have inner walls which are approximately perpendicular to the mirror surface and make planar contacts with the outer surfaces of the outer shells. The adhesive which is used on these contact surfaces tends to contract when it dries but the outer shells can bend and serve to minimize the tendency of the mirror to warp.

Photoreceptors in a primitive mammal, the South American opossum, Didelphis marsupialis aurita: characterization with anti-opsin immunolabeling.

PubMed

Ahnelt, P K; Hokoç, J N; Röhlich, P

1995-01-01

The retinas of placental mammals appear to lack the large number and morphological diversity of cone subtypes found in diurnal reptiles. We have now studied the photoreceptor layer of a South American marsupial (Didelphis marsupialis aurita) by peanut agglutinin labeling of the cone sheath and by labeling of cone outer segments with monoclonal anti-visual pigment antibodies that have been proven to consistently label middle-to-long wavelength (COS-1) and short-wavelength (OS-2) cone subpopulations in placental mammals. Besides a dominant rod population (max. = 400,000/mm2) four subtypes of cones (max. = 3000/mm2) were identified. The outer segments of three cone subtypes were labeled by COS-1: a double cone with a principal cone containing a colorless oil droplet, a single cone with oil droplet, and another single cone. A second group of single cones lacking oil droplets was labeled by OS-2 antibody. The topography of these cone subtypes showed striking anisotropies. The COS-1 labeled single cones without oil droplets were found all over the retina and constituted the dominant population in the area centralis located in the temporal quadrant of the upper, tapetal hemisphere. The population of OS-2 labeled cones was also ubiquitous although slightly higher in the upper hemisphere (200/mm2). The COS-1 labeled cones bearing an oil droplet, including the principal member of double cones, were concentrated (800/mm2) in the inferior, non-tapetal half of the retina. The two spectral types of single cones resemble those of dichromatic photopic systems in most placental mammals. The additional set of COS-1 labeled cones is a distinct marsupial feature. The presence of oil droplets in this cone subpopulation, its absence in the area centralis, and the correlation with the non-tapetal inferior hemisphere suggest a functional specialization, possibly for mesopic conditions. Thus, sauropsid features have been retained but probably with a modified function.

Retinal adaptation to dim light vision in spectacled caimans (Caiman crocodilus fuscus): Analysis of retinal ultrastructure.

PubMed

Karl, Anett; Agte, Silke; Zayas-Santiago, Astrid; Makarov, Felix N; Rivera, Yomarie; Benedikt, Jan; Francke, Mike; Reichenbach, Andreas; Skatchkov, Serguei N; Bringmann, Andreas

2018-05-19

It has been shown that mammalian retinal glial (Müller) cells act as living optical fibers that guide the light through the retinal tissue to the photoreceptor cells (Agte et al., 2011; Franze et al., 2007). However, for nonmammalian species it is unclear whether Müller cells also improve the transretinal light transmission. Furthermore, for nonmammalian species there is a lack of ultrastructural data of the retinal cells, which, in general, delivers fundamental information of the retinal function, i.e. the vision of the species. A detailed study of the cellular ultrastructure provides a basic approach of the research. Thus, the aim of the present study was to investigate the retina of the spectacled caimans at electron and light microscopical levels to describe the structural features. For electron microscopy, we used a superfast microwave fixation procedure in order to achieve more precise ultrastructural information than common fixation techniques. As result, our detailed ultrastructural study of all retinal parts shows structural features which strongly indicate that the caiman retina is adapted to dim light and night vision. Various structural characteristics of Müller cells suppose that the Müller cell may increase the light intensity along the path of light through the neuroretina and, thus, increase the sensitivity of the scotopic vision of spectacled caimans. Müller cells traverse the whole thickness of the neuroretina and thus may guide the light from the inner retinal surface to the photoreceptor cell perikarya and the Müller cell microvilli between the photoreceptor segments. Thick Müller cell trunks/processes traverse the layers which contain light-scattering structures, i.e., nerve fibers and synapses. Large Müller cell somata run through the inner nuclear layer and contain flattened, elongated Müller cell nuclei which are arranged along the light path and, thus, may reduce the loss of the light intensity along the retinal light path. The oblique arrangement of many Müller cell trunks/processes in the inner plexiform layer and the large Müller cell somata in the inner nuclear layer may suggest that light guidance through Müller cells increases the visual sensitivity. Furthermore, an adaptation of the caiman retina to low light levels is strongly supported by detailed ultrastructural data of other retinal parts, e.g. by (i) the presence of a guanine-based retinal tapetum, (ii) the rod dominance of the retina, (iii) the presence of photoreceptor cell nuclei, which penetrate the outer limiting membrane, (iv) the relatively low densities of photoreceptor and neuronal cells which is compensated by (v) the presence of rods with long and thick outer segments, that may increase the probability of photon absorption. According to a cell number analysis, the central and temporal areas of the dorsal tapetal retina, which supports downward prey detection in darker water, are the sites of the highest diurnal contrast/color vision, i.e. cone vision and of the highest retinal light sensitivity, i.e. rod vision. Copyright © 2018 Elsevier Ltd. All rights reserved.

Nuclear reactor safety device

DOEpatents

Hutter, E.

1983-08-15

A safety device is described for use in a nuclear reactor for axially repositioning a control rod with respect to the reactor core in the event of a thermal excursion. It comprises a laminated strip helically configured to form a tube, said tube being in operative relation to said control rod. The laminated strip is formed of at least two materials having different thermal coefficients of expansion, and is helically configured such that the material forming the outer lamina of the tube has a greater thermal coefficient of expansion than the material forming the inner lamina of said tube. In the event of a thermal excursion the laminated strip will tend to curl inwardly so that said tube will increase in length, whereby as said tube increases in length it exerts a force on said control rod to axially reposition said control rod with respect to said core.

Patellar segmentation from 3D magnetic resonance images using guided recursive ray-tracing for edge pattern detection

NASA Astrophysics Data System (ADS)

Cheng, Ruida; Jackson, Jennifer N.; McCreedy, Evan S.; Gandler, William; Eijkenboom, J. J. F. A.; van Middelkoop, M.; McAuliffe, Matthew J.; Sheehan, Frances T.

2016-03-01

The paper presents an automatic segmentation methodology for the patellar bone, based on 3D gradient recalled echo and gradient recalled echo with fat suppression magnetic resonance images. Constricted search space outlines are incorporated into recursive ray-tracing to segment the outer cortical bone. A statistical analysis based on the dependence of information in adjacent slices is used to limit the search in each image to between an outer and inner search region. A section based recursive ray-tracing mechanism is used to skip inner noise regions and detect the edge boundary. The proposed method achieves higher segmentation accuracy (0.23mm) than the current state-of-the-art methods with the average dice similarity coefficient of 96.0% (SD 1.3%) agreement between the auto-segmentation and ground truth surfaces.

Cell and current collector felt arrangement for solid oxide electrochemical cell combinations

DOEpatents

Reichner, Philip

1988-01-01

A solid electrolyte electrochemical cell combination 1 is made, comprising an annular, axially elongated, inner electrode 2 containing at least one interior gas feed conduit 3; annular solid electrolyte segments 4 around and covering portions of the inner electrode; annular outer electrode segments 6 around and covering portions of the electrolyte segments; electronically conducting, non-porous, interconnection material 5 disposed between electrolyte segments and in contact with the inner electrode, and electronically conducting, porous, metal fiber current collector felts 7 disposed on top of the non-porous interconnect material and outer electrode segments, where both the non-porous interconnect material and the porous metal felts are disposed circumferentially about the cell, transversely to the axial length of the cell and the inner electrode is continuous for the entire axial length of the cell combination.

Rod/Coil Block Copolyimides for Ion-Conducting Membranes

NASA Technical Reports Server (NTRS)

Meador, Mary Ann B.; Kinder, James D.

2003-01-01

Rod/coil block copolyimides that exhibit high levels of ionic conduction can be made into diverse products, including dimensionally stable solid electrolyte membranes that function well over wide temperature ranges in fuel cells and in lithium-ion electrochemical cells. These rod/coil block copolyimides were invented to overcome the limitations of polymers now used to make such membranes. They could also be useful in other electrochemical and perhaps some optical applications, as described below. The membranes of amorphous polyethylene oxide (PEO) now used in lithium-ion cells have acceptably large ionic conductivities only at temperatures above 60 C, precluding use in what would otherwise be many potential applications at lower temperatures. PEO is difficult to process, and, except at the highest molecular weights it is not very dimensionally stable. It would be desirable to operate fuel cells at temperatures above 80 C to take advantage of better kinetics of redox reactions and to reduce contamination of catalysts. Unfortunately, proton-conduction performance of a typical perfluorosulfonic polymer membrane now used as a solid electrolyte in a fuel cell decreases with increasing temperature above 80 C because of loss of water from within the membrane. The loss of water has been attributed to the hydrophobic nature of the polymer backbone. In addition, perfluorosulfonic polymers are expensive and are not sufficiently stable for long-term use. Rod/coil block copolyimides are so named because each molecule of such a polymer comprises short polyimide rod segments alternating with flexible polyether coil segments (see figure). The rods and coils can be linear, branched, or mixtures of linear and branched. A unique feature of these polymers is that the rods and coils are highly incompatible, giving rise to a phase separation with a high degree of ordering that creates nanoscale channels in which ions can travel freely. The conduction of ions can occur in the coil phase, the rod phase, or both phases.

Measurement of activation of rhodopsine with heavy ions irradiation in the ALTEA program: a possible mechanism responsible for light flash perceptions in space

NASA Astrophysics Data System (ADS)

Narici, Livio; Rinaldi, Adele; Sannita, Walter, , Prof; Paci, Maurizio; Brunetti, Valentina; de Martino, Angelo; Picozza, Piergiorgio

Since late 60s astronauts in space have reported seeing flashes of light, more frequently when dark adapted. Experiments have been performed to characterize these phenomena, and to suggest possible mechanisms. High Z ions have been shown to be the most likely cause of these perceptions: when ionizing radiation hits the eye there is a high probability of a light flash perception. However the mechanisms behind this phenomenon are not fully understood yet. We show that one of these mechanisms is the activation of the rhodopsin (bleaching) by heavy ions. Rhodopsin is at the start of the photo-electronic cascade in the process of vision. It is one of the best molecular transducer to convert a visible photon into an electric signal. In this work we show that rhodopsine can also be activated by irradiation with 12C nuclei. In the frame of ALTEA program, aimed at studying the effects of cosmic radiation on brain functions, an investigation on the interaction between heavy ions and rhodopsin has been performed. Intact Rod Outer Segment (ROS) containing rhodopsin were isolated from bovine retina. Suspended rods were irradiated with 12C (200 MeV/n, well below the Cherenkov threshold) at GSI (Darmstadt FRG) with doses ranging from few mrem to several rem. Spectrophotometric measurements investigated the presence of non activated and activated rhodopsin. The functionality of the purified rods were checked by previous light irradiation and subsequent regeneration by the addition of external 11-cis-retinal, to confirm the reversibility of the process in vitro. We can show effective and reversible bleaching also following irradiation, thus proving that the rhodopsin was not damaged by radiation. Works are in progress to model this interaction. Latest analysis results and considerations about the underlying mechanism will be presented.

Phagocytosis of photoreceptor outer segments by transplanted human neural stem cells as a neuroprotective mechanism in retinal degeneration.

PubMed

Cuenca, Nicolás; Fernández-Sánchez, Laura; McGill, Trevor J; Lu, Bin; Wang, Shaomei; Lund, Raymond; Huhn, Stephen; Capela, Alexandra

2013-10-15

Transplantation of human central nervous system stem cells (HuCNS-SC) into the subretinal space of Royal College of Surgeons (RCS) rats preserves photoreceptors and visual function. To explore possible mechanism(s) of action underlying this neuroprotective effect, we performed a detailed morphologic and ultrastructure analysis of HuCNS-SC transplanted retinas. The HuCNS-SC were transplanted into the subretinal space of RCS rats. Histologic examination of the transplanted retinas was performed by light and electron microscopy. Areas of the retina adjacent to HuCNS-SC graft (treated regions) were analyzed and compared to control sections obtained from the same retina, but distant from the transplant site (untreated regions). The HuCNS-SC were detected as a layer of STEM 121 immunopositive cells in the subretinal space. In treated regions, preserved photoreceptor nuclei, as well as inner and outer segments were identified readily. In contrast, classic signs of degeneration were observed in the untreated regions. Interestingly, detailed ultrastructure analysis revealed a striking preservation of the photoreceptor-bipolar-horizontal cell synaptic contacts in the outer plexiform layer (OPL) of treated areas, in stark contrast with untreated areas. Finally, the presence of phagosomes and vesicles exhibiting the lamellar structure of outer segments also was detected within the cytosol of HuCNS-SC, indicating that these cells have phagocytic capacity in vivo. This study reveals the novel finding that preservation of specialized synaptic contacts between photoreceptors and second order neurons, as well as phagocytosis of photoreceptor outer segments, are potential mechanism(s) of HuCNS-SC transplantation, mediating functional rescue in retinal degeneration.

Retinal Structure Measurements as Inclusion Criteria for Stem Cell-Based Therapies of Retinal Degenerations.

PubMed

Jacobson, Samuel G; Matsui, Rodrigo; Sumaroka, Alexander; Cideciyan, Artur V

2016-04-01

We reviewed and illustrated the most optimal retinal structural measurements to make in stem cell clinical trials. Optical coherence tomography (OCT) and autofluorescence (AF) imaging were used to evaluate patients with severe visual loss from nonsyndromic and syndromic retinitis pigmentosa (RP), ABCA4-Stargardt disease, and nonneovascular age-related macular degeneration (AMD). Outer nuclear layer (ONL), rod outer segment (ROS) layer, inner retina, ganglion cell layer (GCL), and nerve fiber layer (NFL) thicknesses were quantified. All patients had severely reduced visual acuities. Retinitis pigmentosa patients had limited visual fields; maculopathy patients had central scotomas with retained peripheral function. For the forms of RP illustrated, there was detectable albeit severely reduced ONL across the scanned retina, and normal or hyperthick GCL and NFL. Maculopathy patients had no measurable ONL centrally; it became detectable with eccentricity. Some maculopathy patients showed unexpected GCL losses. Autofluorescence imaging illustrated central losses of RPE integrity. A hypothetical scheme to relate patient data with different phases of retinal remodeling in animal models of retinal degeneration was presented. Stem cell science is advancing, but it is not too early to open the discussion of criteria for patient selection and monitoring. Available clinical tools, such as OCT and AF imaging, can provide inclusion/exclusion criteria and robust objective outcomes. Accepting that early trials may not lead to miraculous cures, we should be prepared to know why-scientifically and clinically-so we can improve subsequent trials. We also must determine if retinal remodeling is an impediment to efficacy.

Coherent Anti-Stokes Raman Scattering (CARS) Microscopy: A Novel Technique for Imaging the Retina

PubMed Central

Masihzadeh, Omid; Ammar, David A.; Kahook, Malik Y.; Lei, Tim C.

2013-01-01

Purpose. To image the cellular and noncellular structures of the retina in an intact mouse eye without the application of exogenous fluorescent labels using noninvasive, nondestructive techniques. Methods. Freshly enucleated mouse eyes were imaged using two nonlinear optical techniques: coherent anti-Stokes Raman scattering (CARS) and two-photon autofluorescence (TPAF). Cross sectional transverse sections and sequential flat (en face) sagittal sections were collected from a region of sclera approximately midway between the limbus and optic nerve. Imaging proceeded from the surface of the sclera to a depth of ∼60 μm. Results. The fluorescent signal from collagen fibers within the sclera was evident in the TPAF channel; the scleral collagen fibers showed no organization and appeared randomly packed. The sclera contained regions lacking TPAF and CARS fluorescence of ∼3 to 15 μm in diameter that could represent small vessels or scleral fibroblasts. Intense punctate CARS signals from the retinal pigment epithelial layer were of a size and shape of retinyl storage esters. Rod outer segments could be identified by the CARS signal from their lipid-rich plasma membranes. Conclusions. CARS microscopy can be used to image the outer regions of the mammalian retina without the use of a fluorescent dye or exogenously expressed recombinant protein. With technical advancements, CARS/TPAF may represent a new avenue for noninvasively imaging the retina and might complement modalities currently used in clinical practice. PMID:23580484

3D printed phantoms of retinal photoreceptor cells for evaluating adaptive optics imaging modalities

NASA Astrophysics Data System (ADS)

Kedia, Nikita; Liu, Zhuolin; Sochol, Ryan; Hammer, Daniel X.; Agrawal, Anant

2018-02-01

Adaptive optics-enabled optical coherence tomography (AO-OCT) and scanning laser ophthalmoscopy (AO-SLO) devices can resolve retinal cones and rods in three dimensions. To evaluate the improved resolution of AO-OCT and AO-SLO, a phantom that mimics retinal anatomy at the cellular level is required. We used a two-photon polymerization approach to fabricate three-dimensional (3D) photoreceptor phantoms modeled on the central foveal cones. By using a femtosecond laser to selectively photocure precise locations within a liquid-based photoresist via two-photon absorption, we produced high-resolution phantoms with μm-level dimensions similar to true anatomy. In this work, we present two phantoms to evaluate the resolution limits of an AO imaging system: one that models only the outer segments of the photoreceptor cells at varying retinal eccentricities and another that contains anatomically relevant features of the full-length photoreceptor. With these phantoms we are able to quantitatively estimate transverse resolution of an AO system and produce images that are comparable to those found in the human retina.

Omnidirectional wheel

NASA Technical Reports Server (NTRS)

Blumrich, J. F. (Inventor)

1974-01-01

The apparatus consists of a wheel having a hub with radially disposed spokes which are provided with a plurality of circumferential rim segments. These rim segments carry, between the spokes, rim elements which are rigid relative to their outer support surfaces, and defined in their outer contour to form a part of the circle forming the wheel diameter. The rim segments have provided for each of the rim elements an independent drive means selectively operable when the element is in ground contact to rotatably drive the rim element in a direction of movement perpendicularly lateral to the normal plane of rotation and movement of the wheel. This affords the wheel omnidirectional movement.

Mechanical and degradation properties of biodegradable Mg strengthened poly-lactic acid composite through plastic injection molding.

PubMed

Butt, Muhammad Shoaib; Bai, Jing; Wan, Xiaofeng; Chu, Chenglin; Xue, Feng; Ding, Hongyan; Zhou, Guanghong

2017-01-01

Full biodegradable magnesium alloy (AZ31) strengthened poly-lactic acid (PLA) composite rods for potential application for bone fracture fixation were prepared by plastic injection process in this work. Their surface/interfacial morphologies, mechanical properties and vitro degradation were studied. In comparison with untreated Mg rod, porous MgO ceramic coating on Mg surface formed by Anodizing (AO) and micro-arc-oxidation (MAO)treatment can significantly improve the interfacial binding between outer PLA cladding and inner Mg rod due to the micro-anchoring action, leading to better mechanical properties and degradation performance of the composite rods.With prolonging immersion time in simulated body fluid (SBF) solution until 8weeks, the MgO porous coating were corroded gradually, along with the disappearance of original pores and the formation of a relatively smooth surface. This resulted in a rapidly reduction in mechanical properties for corresponding composite rods owing to the weakening of interfacial binding capacity. The present results indicated that this new PLA-clad Mg composite rods show good potential biomedical applications for implants and instruments of orthopedic inner fixation. Copyright © 2016 Elsevier B.V. All rights reserved.

Progression of neuronal and synaptic remodeling in the rd10 mouse model of retinitis pigmentosa.

PubMed

Phillips, M Joseph; Otteson, Deborah C; Sherry, David M

2010-06-01

The Pde6b(rd10) (rd10) mouse has a moderate rate of photoreceptor degeneration and serves as a valuable model for human autosomal recessive retinitis pigmentosa (RP). We evaluated the progression of neuronal remodeling of second- and third-order retinal cells and their synaptic terminals in retinas from Pde6b(rd10) (rd10) mice at varying stages of degeneration ranging from postnatal day 30 (P30) to postnatal month 9.5 (PNM9.5) using immunolabeling for well-known cell- and synapse-specific markers. Following photoreceptor loss, changes occurred progressively from outer to inner retina. Horizontal cells and rod and cone bipolar cells underwent morphological remodeling that included loss of dendrites, cell body migration, and the sprouting of ectopic processes. Gliosis, characterized by translocation of Müller cell bodies to the outer retina and thickening of their processes, was evident by P30 and became more pronounced as degeneration progressed. Following rod degeneration, continued expression of VGluT1 in the outer retina was associated with survival and expression of synaptic proteins by nearby second-order neurons. Rod bipolar cell terminals showed a progressive reduction in size and ectopic bipolar cell processes extended into the inner nuclear layer and ganglion cell layer by PNM3.5. Putative ectopic conventional synapses, likely arising from amacrine cells, were present in the inner nuclear layer by PNM9.5. Despite these changes, the laminar organization of bipolar and amacrine cells and the ON-OFF organization in the inner plexiform layer was largely preserved. Surviving cone and bipolar cell terminals continued to express the appropriate cell-specific presynaptic proteins needed for synaptic function up to PNM9.5. (c) 2010 Wiley-Liss, Inc.

Progression of Neuronal and Synaptic Remodeling in the rd10 Mouse Model of Retinitis Pigmentosa

PubMed Central

Phillips, M. Joseph; Otteson, Deborah C.; Sherry, David M.

2010-01-01

The Pde6brd10 (rd10) mouse has a moderate rate of photoreceptor degeneration and serves as a valuable model for human autosomal recessive retinitis pigmentosa (RP). We evaluated the progression of neuronal remodeling of second- and third-order retinal cells and their synaptic terminals in retinas from Pde6brd10 (rd10) mice at varying stages of degeneration ranging from postnatal day 30 (P30) to postnatal month 9.5 (PNM9.5) using immunolabeling for well known cell- and synapse-specific markers. Following photoreceptor loss, changes occurred progressively from outer to inner retina. Horizontal cells and rod and cone bipolar cells underwent morphological remodeling that included loss of dendrites, cell body migration, and the sprouting of ectopic processes. Gliosis, characterized by translocation of Müller cell bodies to the outer retina and thickening of their processes, was evident by P30 and became more pronounced as degeneration progressed. Following rod degeneration, continued expression of VGluT1 in the outer retina was associated with survival and expression of synaptic proteins by nearby second-order neurons. Rod bipolar cell terminals showed a progressive reduction in size and ectopic bipolar cell processes extended into the inner nuclear layer and ganglion cell layer by PNM3.5. Putative ectopic conventional synapses, likely arising from amacrine cells, were present in the inner nuclear layer by PNM9.5. Despite these changes, the laminar organization of bipolar and amacrine cells and the ON-OFF organization in the inner plexiform layer was largely preserved. Surviving cone and bipolar cell terminals continued to express the appropriate cell-specific presynaptic proteins needed for synaptic function up to PNM9.5. PMID:20394059

Transient spectral domain optical coherence tomography findings in classic MEWDS: a case report.

PubMed

Lavigne, Luciana Castro; Isaac, David Leonardo Cruvinel; Duarte Júnior, José Osório; Avila, Marcos Pereira de

2014-01-01

The purpose of this study was to describe a patient with multiple evanescent white dot syndrome (MEWDS) who presented with classic retinal findings and transient changes in outer retinal anatomy. A 20-year-old man presented with mild blurred vision in the left eye, reporting flu-like symptoms 1 week before the visual symptoms started. Fundus examination of the left eye revealed foveal granularity and multiple scattered spots deep to the retina in the posterior pole. Fluorescein angiography and indocyanine green angiography showed typical MEWDS findings. Spectral Domain Optical Coherence Tomography has shown transient changes in outer retinal anatomy with disappearance of inner segment-outer segment junction and mild attenuation of external limiting membrane. Six months later, Spectral Domain Optical Coherence Tomography has shown complete resolution with recovery of normal outer retinal aspect.

Crystallographic Studies of Intermediate Filament Proteins.

PubMed

Guzenko, Dmytro; Chernyatina, Anastasia A; Strelkov, Sergei V

Intermediate filaments (IFs), together with microtubules and actin microfilaments, are the three main cytoskeletal components in metazoan cells. IFs are formed by a distinct protein family, which is made up of 70 members in humans. Most IF proteins are tissue- or organelle-specific, which includes lamins, the IF proteins of the nucleus. The building block of IFs is an elongated dimer, which consists of a central α-helical 'rod' domain flanked by flexible N- and C-terminal domains. The conserved rod domain is the 'signature feature' of the IF family. Bioinformatics analysis reveals that the rod domain of all IF proteins contains three α-helical segments of largely conserved length, interconnected by linkers. Moreover, there is a conserved pattern of hydrophobic repeats within each segment, which includes heptads and hendecads. This defines the presence of both left-handed and almost parallel coiled-coil regions along the rod length. Using X-ray crystallography on multiple overlapping fragments of IF proteins, the atomic structure of the nearly complete rod domain has been determined. Here, we discuss some specific challenges of this procedure, such as crystallization and diffraction data phasing by molecular replacement. Further insights into the structure of the coiled coil and the terminal domains have been obtained using electron paramagnetic resonance measurements on the full-length protein, with spin labels attached at specific positions. This atomic resolution information, as well as further interesting findings, such as the variation of the coiled-coil stability along the rod length, provide clues towards interpreting the data on IF assembly, collected by a range of methods. However, a full description of this process at the molecular level is not yet at hand.

Near equilibrium dynamics of nonhomogeneous Kirchhoff filaments in viscous media

NASA Astrophysics Data System (ADS)

Fonseca, A. F.; de Aguiar, M. A.

2001-01-01

We study the near equilibrium dynamics of nonhomogeneous elastic filaments in viscous media using the Kirchhoff model of rods. Viscosity is incorporated in the model as an external force, which we approximate by the resistance felt by an infinite cylinder immersed in a slowly moving fluid. We use the recently developed method of Goriely and Tabor [Phys. Rev. Lett. 77, 3537 (1996); Physica D 105, 20 (1997); 105, 45 (1997)] to study the dynamics in the vicinity of the simplest equilibrium solution for a closed rod with nonhomogeneous distribution of mass, namely, the planar ring configuration. We show that small variations of the mass density along the rod are sufficient to couple the symmetric modes of the homogeneous rod problem, producing asymmetric deformations that modify substantially the dynamical coiling, even at quite low Reynolds number. The higher-density segments of the rod tend to become more rigid and less coiled. We comment on possible applications to DNA.

Near equilibrium dynamics of nonhomogeneous Kirchhoff filaments in viscous media.

PubMed

Fonseca, A F; de Aguiar, M A

2001-01-01

We study the near equilibrium dynamics of nonhomogeneous elastic filaments in viscous media using the Kirchhoff model of rods. Viscosity is incorporated in the model as an external force, which we approximate by the resistance felt by an infinite cylinder immersed in a slowly moving fluid. We use the recently developed method of Goriely and Tabor [Phys. Rev. Lett. 77, 3537 (1996); Physica D 105, 20 (1997); 105, 45 (1997)] to study the dynamics in the vicinity of the simplest equilibrium solution for a closed rod with nonhomogeneous distribution of mass, namely, the planar ring configuration. We show that small variations of the mass density along the rod are sufficient to couple the symmetric modes of the homogeneous rod problem, producing asymmetric deformations that modify substantially the dynamical coiling, even at quite low Reynolds number. The higher-density segments of the rod tend to become more rigid and less coiled. We comment on possible applications to DNA.

Retractable Visual Indicator Assembly

NASA Technical Reports Server (NTRS)

Hackler, George R. (Inventor); Gamboa, Ronald J. (Inventor); Dominquez, Victor (Inventor)

1998-01-01

A retractable indicator assembly may be mounted on a container which transmits air through the container and removes deleterious gases with an activated charcoal medium in the container. The assembly includes: an elongate indicator housing has a chamber therein; a male adaptor with an external threads is used for sealing engagement with the container; a plug located at the upper end of the housing; a housing that includes a transparent wall portion for viewing at least a portion of the chamber; a litmus indicator, moveable by a retractable rod from a retracted position within the container to an extended position within the chamber of the housing; and an outer housing that is secured to the upper end of the rod, and protects the indicator housing while the litmus indicator is in its normally retracted position. The assembly may be manually manipulated between its extended position wherein the litmus indicator may be viewed through the transparent wall of the indicator housing, and a retracted position wherein the outer housing encloses the indicator housing and engages the exterior of the container.

Characterization of Ether-à-go-go Channels Present in Photoreceptors Reveals Similarity to IKx, a K+ Current in Rod Inner Segments

PubMed Central

Frings, Stephan; Brüll, Nicole; Dzeja, Claudia; Angele, Albert; Hagen, Volker; Kaupp, U. Benjamin; Baumann, Arnd

1998-01-01

In this study, we describe two splice variants of an ether-à-go-go (EAG) K+ channel cloned from bovine retina: bEAG1 and bEAG2. The bEAG2 polypeptide contains an additional insertion of 27 amino acids in the extracellular linker between transmembrane segments S3 and S4. The heterologously expressed splice variants differ in their activation kinetics and are differently modulated by extracellular Mg2+. Cooperativity of modulation by Mg2+ suggests that each subunit of the putative tetrameric channel binds a Mg2+ ion. The channels are neither permeable to Ca2+ ions nor modulated by cyclic nucleotides. In situ hybridization localizes channel transcripts to photoreceptors and retinal ganglion cells. Comparison of EAG currents with IKx, a noninactivating K+ current in the inner segment of rod photoreceptors, reveals an intriguing similarity, suggesting that EAG polypeptides are involved in the formation of Kx channels. PMID:9524140

Current strategies for the restoration of adequate lordosis during lumbar fusion

PubMed Central

Barrey, Cédric; Darnis, Alice

2015-01-01

Not restoring the adequate lumbar lordosis during lumbar fusion surgery may result in mechanical low back pain, sagittal unbalance and adjacent segment degeneration. The objective of this work is to describe the current strategies and concepts for restoration of adequate lordosis during fusion surgery. Theoretical lordosis can be evaluated from the measurement of the pelvic incidence and from the analysis of spatial organization of the lumbar spine with 2/3 of the lordosis given by the L4-S1 segment and 85% by the L3-S1 segment. Technical aspects involve patient positioning on the operating table, release maneuvers, type of instrumentation used (rod, screw-rod connection, interbody cages), surgical sequence and the overall surgical strategy. Spinal osteotomies may be required in case of fixed kyphotic spine. AP combined surgery is particularly efficient in restoring lordosis at L5-S1 level and should be recommended. Finally, not one but several strategies may be used to achieve the need for restoration of adequate lordosis during fusion surgery. PMID:25621216

Zone heated diesel particulate filter electrical connection

DOEpatents

Gonze, Eugene V.; Paratore, Jr., Michael J.

2010-03-30

An electrical connection system for a particulate filter is provided. The system includes: a particulate filter (PF) disposed within an outer shell wherein the PF is segmented into a plurality of heating zones; an outer mat disposed between the particulate filter and the outer shell; an electrical connector coupled to the outer shell of the PF; and a plurality of printed circuit connections that extend along the outer surface of the PF from the electrical connector to the plurality of heating zones.

Matrix metalloproteinase-9 and -2 enhance the ligand sensitivity of photoreceptor cyclic nucleotide-gated channels.

PubMed

Meighan, Peter C; Meighan, Starla E; Rich, Elizabeth D; Brown, R Lane; Varnum, Michael D

2012-01-01

Photoreceptor cyclic nucleotide-gated (CNG) channels are the principal ion channels responsible for transduction of the light-induced change in cGMP concentration into an electrical signal. The ligand sensitivity of photoreceptor CNG channels is subject to regulation by intracellular signaling effectors, including calcium-calmodulin, tyrosine kinases and phosphoinositides. Little is known, however, about regulation of channel activity by modification to extracellular regions of CNG channel subunits. Extracellular proteases MMP9 and -2 are present in the interphotoreceptor matrix adjacent to photoreceptor outer segments. Given that MMPs have been implicated in retinal dysfunction and degeneration, we hypothesized that MMP activity may alter the functional properties of photoreceptor CNG channels. For heterologously expressed rod and cone CNG channels, extracellular exposure to MMPs dramatically increased the apparent affinity for cGMP and the efficacy of cAMP. These changes to ligand sensitivity were not prevented by destabilization of the actin cytoskeleton or by disruption of integrin mediated cell adhesion, but could be attenuated by inhibition of MMP catalytic activity. MMP-mediated gating changes exhibited saturable kinetic properties consistent with enzymatic processing of the CNG channels. In addition, exposure to MMPs decreased the abundance of full-length expressed CNGA3 subunits, with a concomitant increase in putative degradation products. Similar gating effects and apparent proteolysis were observed also for native rod photoreceptor CNG channels. Furthermore, constitutive apparent proteolysis of retinal CNGA1 and retinal MMP9 levels were both elevated in aged mice compared with young mice. Together, these results provide evidence that MMP-mediated proteolysis can regulate the ligand sensitivity of CNG channels.

Matrix metalloproteinase-9 and -2 enhance the ligand sensitivity of photoreceptor cyclic nucleotide-gated channels

PubMed Central

Meighan, Peter C.; Meighan, Starla E.; Rich, Elizabeth D.; Brown, R. Lane; Varnum, Michael D.

2012-01-01

Photoreceptor cyclic nucleotide-gated (CNG) channels are the principal ion channels responsible for transduction of the light-induced change in cGMP concentration into an electrical signal. The ligand sensitivity of photoreceptor CNG channels is subject to regulation by intracellular signaling effectors, including calcium-calmodulin, tyrosine kinases and phosphoinositides. Little is known, however, about regulation of channel activity by modification to extracellular regions of CNG channel subunits. Extracellular proteases MMP9 and -2 are present in the interphotoreceptor matrix adjacent to photoreceptor outer segments. Given that MMPs have been implicated in retinal dysfunction and degeneration, we hypothesized that MMP activity may alter the functional properties of photoreceptor CNG channels. For heterologously expressed rod and cone CNG channels, extracellular exposure to MMPs dramatically increased the apparent affinity for cGMP and the efficacy of cAMP. These changes to ligand sensitivity were not prevented by destabilization of the actin cytoskeleton or by disruption of integrin mediated cell adhesion, but could be attenuated by inhibition of MMP catalytic activity. MMP-mediated gating changes exhibited saturable kinetic properties consistent with enzymatic processing of the CNG channels. In addition, exposure to MMPs decreased the abundance of full-length expressed CNGA3 subunits, with a concomitant increase in putative degradation products. Similar gating effects and apparent proteolysis were observed also for native rod photoreceptor CNG channels. Furthermore, constitutive apparent proteolysis of retinal CNGA1 and retinal MMP9 levels were both elevated in aged mice compared with young mice. Together, these results provide evidence that MMP-mediated proteolysis can regulate the ligand sensitivity of CNG channels. PMID:22699690

CNGA3 deficiency affects cone synaptic terminal structure and function and leads to secondary rod dysfunction and degeneration.

PubMed

Xu, Jianhua; Morris, Lynsie M; Michalakis, Stylianos; Biel, Martin; Fliesler, Steven J; Sherry, David M; Ding, Xi-Qin

2012-03-01

To investigate rod function and survival after cone dysfunction and degeneration in a mouse model of cone cyclic nucleotide-gated (CNG) channel deficiency. Rod function and survival in mice with cone CNG channel subunit CNGA3 deficiency (CNGA3-/- mice) were evaluated by electroretinographic (ERG), morphometric, and Western blot analyses. The arrangement, integrity, and ultrastructure of photoreceptor terminals were investigated by immunohistochemistry and electron microscopy. The authors found loss of cone function and cone death accompanied by impairment of rods and rod-driven signaling in CNGA3-/- mice. Scotopic ERG b-wave amplitudes were reduced by 15% at 1 month, 30% at 6 months, and 40% at 9 months and older, while scotopic a-wave amplitudes were decreased by 20% at 9 months, compared with ERGs of age-matched wild-type mice. Outer nuclear layer thickness in CNGA3-/- retina was reduced by 15% at 12 months compared with age-matched wild-type controls. This was accompanied by a 30%-40% reduction in expression of rod-specific proteins, including rhodopsin, rod transducin α-subunit, and glutamic acid-rich protein (GARP). Cone terminals in the CNGA3-/- retina showed a progressive loss of neurochemical and ultrastructural integrity. Abnormalities were observed as early as 1 month. Disorganized rod terminal ultrastructure was noted by 12 months. These findings demonstrate secondary rod impairment and degeneration after cone degeneration in mice with cone CNG channel deficiency. Loss of cone phototransduction accompanies the compromised integrity of cone terminals. With time, rod synaptic structure, function, and viability also become compromised.

Lunar drill footplate and casing

NASA Technical Reports Server (NTRS)

Maassen, Erik C.; Hendrix, Thomas H.; Morrison, Eddie W.; Phillips, Rodrick B.; Le, Vu Quang; Works, Bruce A.

1989-01-01

To prevent hole collapse during lunar drilling operations, a casing has been devised of a graphite reinforced polyimide composite which will be able to withstand the lunar environment. Additionally, this casing will be inserted into the ground in segments two meters long which will penetrate the regolith simultaneously with the auger. The vertical action of the mobile platform will provide a downward force to the casing string through a special adaptor, giving the casing the needed impetus to sink the anticipated depth of ten meters. Casing segments will be connected with a simple snap arrangement. Excess casing will be cut off by a cylindrical cutting tool which will also transport the excess casing away from the hole. A footplate will be incorporated to grasp the auger rod string during rod segment additions or removals. The footplate grasping mechanism will consist of a set of vice-like arms, one end of each bearing threaded to a common power screw. The power screw will be threaded such that one end's thread pitch opposes that of the other end. The weight of the auger and rod string will be transmitted through the arms to the power screw and absorbed by a set of three ball bearing assemblies. The power screw will be driven by a one-half horsepower brushless motor actuated by radio control. The footplate will rest on four short legs and be anchored with pins that are an integral part of each leg.

Fail-safe storage rack for irradiated fuel rod assemblies

DOEpatents

Lewis, D.R.

1993-03-23

A fail-safe storage rack is provided for interim storage of spent but radioactive nuclear fuel rod assemblies. The rack consists of a checkerboard array of substantially square, elongate receiving tubes fully enclosed by a double walled container, the outer wall of which is imperforate for liquid containment and the inner wall of which is provided with perforations for admitting moderator liquid flow to the elongate receiving tubes, the liquid serving to take up waste heat from the stored nuclear assemblies and dissipate same to the ambient liquid reservoir. A perforated cover sealing the rack facilitates cooling liquid entry and dissipation.

Fail-safe storage rack for irradiated fuel rod assemblies

DOEpatents

Lewis, Donald R.

1993-01-01

A fail-safe storage rack is provided for interim storage of spent but radioactive nuclear fuel rod assemblies. The rack consists of a checkerboard array of substantially square, elongate receiving tubes fully enclosed by a double walled container, the outer wall of which is imperforate for liquid containment and the inner wall of which is provided with perforations for admitting moderator liquid flow to the elongate receiving tubes, the liquid serving to take up waste heat from the stored nuclear assemblies and dissipate same to the ambient liquid reservoir. A perforated cover sealing the rack facilitates cooling liquid entry and dissipation.

Form, shape and function: segmented blood flow in the choriocapillaris

PubMed Central

Zouache, M. A.; Eames, I.; Klettner, C. A.; Luthert, P. J.

2016-01-01

The development of fluid transport systems was a key event in the evolution of animals and plants. While within vertebrates branched geometries predominate, the choriocapillaris, which is the microvascular bed that is responsible for the maintenance of the outer retina, has evolved a planar topology. Here we examine the flow and mass transfer properties associated with this unusual geometry. We show that as a result of the form of the choriocapillaris, the blood flow is decomposed into a tessellation of functional vascular segments of various shapes delineated by separation surfaces across which there is no flow, and in the vicinity of which the transport of passive substances is diffusion-limited. The shape of each functional segment is determined by the distribution of arterioles and venules and their respective relative flow rates. We also show that, remarkably, the mass exchange with the outer retina is a function of the shape of each functional segment. In addition to introducing a novel framework in which the structure and function of the metabolite delivery system to the outer retina may be investigated in health and disease, the present work provides a general characterisation of the flow and transfers in multipole Hele-Shaw configurations. PMID:27779198

Segmented annular combustor

DOEpatents

Reider, Samuel B.

1979-01-01

An industrial gas turbine engine includes an inclined annular combustor made up of a plurality of support segments each including inner and outer walls of trapezoidally configured planar configuration extents and including side flanges thereon interconnected by means of air cooled connector bolt assemblies to form a continuous annular combustion chamber therebetween and wherein an air fuel mixing chamber is formed at one end of the support segments including means for directing and mixing fuel within a plenum and a perforated header plate for directing streams of air and fuel mixture into the combustion chamber; each of the outer and inner walls of each of the support segments having a ribbed lattice with tracks slidably supporting porous laminated replaceable panels and including pores therein for distributing combustion air into the combustion chamber while cooling the inner surface of each of the panels by transpiration cooling thereof.

Directional sensitivity of the retina: A layered scattering model of outer-segment photoreceptor pigments

PubMed Central

Vohnsen, Brian

2014-01-01

Photoreceptor outer segments have been modeled as stacked arrays of discs or membrane infoldings containing visual pigments with light-induced dipole moments. Waveguiding has been excluded so fields diffract beyond the physical boundaries of each photoreceptor cell. Optical reciprocity is used to argue for identical radiative and light gathering properties of pigments to model vision. Two models have been introduced: one a macroscopic model that assumes a uniform pigment density across each layer and another microscopic model that includes the spatial location of each pigment molecule within each layer. Both models result in highly similar directionality at the pupil plane which proves to be insensitive to the exact details of the outer-segment packing being predominantly determined by the first and last contributing layers as set by the fraction of bleaching. The versatility of the microscopic model is demonstrated with an array of examples that includes the Stiles-Crawford effect, visibility of a focused beam of light and the role of defocus. PMID:24877016

Photoreceptor Outer Segment-like Structures in Long-Term 3D Retinas from Human Pluripotent Stem Cells.

PubMed

Wahlin, Karl J; Maruotti, Julien A; Sripathi, Srinivasa R; Ball, John; Angueyra, Juan M; Kim, Catherine; Grebe, Rhonda; Li, Wei; Jones, Bryan W; Zack, Donald J

2017-04-10

The retinal degenerative diseases, which together constitute a leading cause of hereditary blindness worldwide, are largely untreatable. Development of reliable methods to culture complex retinal tissues from human pluripotent stem cells (hPSCs) could offer a means to study human retinal development, provide a platform to investigate the mechanisms of retinal degeneration and screen for neuroprotective compounds, and provide the basis for cell-based therapeutic strategies. In this study, we describe an in vitro method by which hPSCs can be differentiated into 3D retinas with at least some important features reminiscent of a mature retina, including exuberant outgrowth of outer segment-like structures and synaptic ribbons, photoreceptor neurotransmitter expression, and membrane conductances and synaptic vesicle release properties consistent with possible photoreceptor synaptic function. The advanced outer segment-like structures reported here support the notion that 3D retina cups could serve as a model for studying mature photoreceptor development and allow for more robust modeling of retinal degenerative disease in vitro.

Cone arrestin: deciphering the structure and functions of arrestin 4 in vision.

PubMed

Craft, Cheryl Mae; Deming, Janise D

2014-01-01

Cone arrestin (Arr4) was discovered 20 years ago as a human X-chromosomal gene that is highly expressed in pinealocytes and cone photoreceptors. Subsequently, specific antibodies were developed to identify Arr4 and to distinguish cone photoreceptor morphology in health and disease states. These reagents were used to demonstrate Arr4 translocation from cone inner segments in the dark to outer segments with light stimulation, similarly to Arrestin 1 (Arr1) translocation in rod photoreceptors. A decade later, the Arr4 crystal structure was solved, which provided more clues about Arr4's mechanisms of action. With the creation of genetically engineered visual arrestin knockout mice, one critical function of Arr4 was clarified. In single living cones, both visual arrestins bind to light-activated, G protein receptor kinase 1 (Grk1) phosphorylated cone opsins to desensitize them, and in their absence, mouse cone pigment shutoff is delayed. Still under investigation are additional functions; however, it is clear that Arr4 has non-opsin-binding partners and diverse synaptic roles, including cellular anchoring and trafficking. Recent studies reveal Arr4 is involved in high temporal resolution and contrast sensitivity, which opens up a new direction for research on this intriguing protein. Even more exciting is the potential for therapeutic use of the Arr4 promoter with an AAV-halorhodopsin that was shown to be effective in using the remaining cones in retinal degeneration mouse models to drive inner retinal circuitry for motion detection and light/dark discrimination.

Biomechanical advantages of supplemental accessory and satellite rods with and without interbody cages implantation for the stabilization of pedicle subtraction osteotomy.

PubMed

La Barbera, Luigi; Brayda-Bruno, Marco; Liebsch, Christian; Villa, Tomaso; Luca, Andrea; Galbusera, Fabio; Wilke, Hans-Joachim

2018-05-08

To investigate the effect of anterior interbody cages, accessory and satellite rods usage on primary stability and rod strains for PSO stabilization. Seven human cadaveric spine segments (T12-S1) underwent PSO at L4 with posterior fixation from L2 to S1. In vitro flexibility tests were performed under pure moments in flexion/extension (FE), lateral bending (LB) and axial rotation (AR) to determine the range of motion, while measuring the strains on the primary rods with strain gauge rosettes. Six constructs with 2, 3 and 4 rods, with and without interbody cages implantation adjacent to the PSO site, were compared. All constructs had comparable effects in reducing spine kinematics compared to the intact condition (- 94% in FE and LB; - 80% in AR). Supplementation of 2 rods with lateral accessory rods (4 rods) was the most effective strategy in minimizing primary rod strains, particularly when coupled to cages (p ≤ 0.005; - 50% in FE, - 42% in AR and - 11% in LB); even without cages, the strains were significantly reduced (p ≤ 0.009; - 26%, - 37%, - 9%). The addition of a central satellite rod with laminar hooks (3 rods) effectively reduced rod strains in FE (p ≤ 0.005; - 30%) only in combination with cages. The study supports the current clinical practice providing a strong biomechanical rationale to recommend 4-rod constructs based on accessory rods combined with cages adjacent to PSO site. Although weaker, the usage of accessory rods without cages and of a central satellite rod with hooks in combination with interbody spacers may also be justified. These slides can be retrieved under Electronic Supplementary Material.

Inner Segment Remodeling and Mitochondrial Translocation in Cone Photoreceptors in Age-Related Macular Degeneration With Outer Retinal Tubulation.

PubMed

Litts, Katie M; Messinger, Jeffrey D; Freund, K Bailey; Zhang, Yuhua; Curcio, Christine A

2015-04-01

To quantify impressions of mitochondrial translocation in degenerating cones and to determine the nature of accumulated material in the subretinal space with apparent inner segment (IS)-like features by examining cone IS ultrastructure. Human donor eyes with advanced age-related macular degeneration (AMD) were screened for outer retinal tubulation (ORT) in macula-wide, high-resolution digital sections. Degenerating cones inside ORT (ORT cones) and outside ORT (non-ORT cones) from AMD eyes and unaffected cones in age-matched control eyes were imaged using transmission electron microscopy. The distances of mitochondria to the external limiting membrane (ELM), cone IS length, and cone IS width at the ELM were measured. Outer retinal tubulation and non-ORT cones lose outer segments (OS), followed by shortening of IS and mitochondria. In non-ORT cones, IS broaden. Outer retinal tubulation and non-ORT cone IS myoids become undetectable due to mitochondria redistribution toward the nucleus. Some ORT cones were found lacking IS and containing mitochondria in the outer fiber (between soma and ELM). Unlike long, thin IS mitochondria in control cones, ORT and non-ORT IS mitochondria are ovoid or reniform. Shed IS, some containing mitochondria, were found in the subretinal space. In AMD, macula cones exhibit loss of detectable myoid due to IS shortening in addition to OS loss, as described. Mitochondria shrink and translocate toward the nucleus. As reflectivity sources, translocating mitochondria may be detectable using in vivo imaging to monitor photoreceptor degeneration in retinal disorders. These results improve the knowledge basis for interpreting high-resolution clinical retinal imaging.

Crippling Strength of Axially Loaded Rods

NASA Technical Reports Server (NTRS)

Natalis, FR

1921-01-01

A new empirical formula was developed that holds good for any length and any material of a rod, and agrees well with the results of extensive strength tests. To facilitate calculations, three tables are included, giving the crippling load for solid and hollow sectioned wooden rods of different thickness and length, as well as for steel tubes manufactured according to the standards of Army Air Services Inspection. Further, a graphical method of calculation of the breaking load is derived in which a single curve is employed for determination of the allowable fiber stress. Finally, the theory is discussed of the elastic curve for a rod subject to compression, according to which no deflection occurs, and the apparent contradiction of this conclusion by test results is attributed to the fact that the rods under test are not perfectly straight, or that the wall thickness and the material are not uniform. Under the assumption of an eccentric rod having a slight initial bend according to a sine curve, a simple formula for the deflection is derived, which shows a surprising agreement with test results. From this a further formula is derived for the determination of the allowable load on an eccentric rod. The resulting relations are made clearer by means of a graphical representation of the relation of the moments of the outer and inner forces to the deflection.

Individual Trabecula Segmentation (ITS)-Based Morphological Analyses and Micro Finite Element Analysis of HR-pQCT Images Discriminate Postmenopausal Fragility Fractures Independent of DXA Measurements

PubMed Central

Liu, X. Sherry; Stein, Emily M.; Zhou, Bin; Zhang, Chiyuan A.; Nickolas, Thomas L.; Cohen, Adi; Thomas, Valerie; McMahon, Donald J.; Cosman, Felicia; Nieves, Jeri; Shane, Elizabeth; Guo, X. Edward

2011-01-01

Osteoporosis is typically diagnosed by dual energy x-ray absorptiometry (DXA) measurements of areal bone mineral density (aBMD). Emerging technologies, such as high-resolution peripheral quantitative computed tomography (HR-pQCT), may increase the diagnostic accuracy of DXA and enhance our mechanistic understanding of decreased bone strength in osteoporosis. Women with (n=68) and without (n=101) a history of postmenopausal fragility fracture had aBMD measured by DXA, trabecular plate and rod microarchitecture measured by HR-pQCT image-based individual trabeculae segmentation (ITS) analysis, and whole bone and trabecular bone stiffness by micro finite element analysis (μFEA) of HR-pQCT images at the radius and tibia. DXA T-scores were similar in women with and without fractures at the spine, hip and 1/3 radius, but lower in fracture subjects at the ultradistal radius. Trabecular microarchitecture of fracture subjects was characterized by preferential reductions in trabecular plate bone volume, number, and connectivity over rod trabecular parameters, loss of axially aligned trabeculae, and a more rod-like trabecular network. In addition, decreased thickness and size of trabecular plates were observed at the tibia. The differences between groups were greater at the radius than the tibia for plate number, rod bone volume fraction and number and plate-rod and rod-rod junction densities. Most differences between groups remained after adjustment for T-score by DXA. At a fixed bone volume fraction, trabecular plate volume, number and connectivity were directly associated with bone stiffness. In contrast, rod volume, number and connectivity were inversely associated with bone stiffness. In summary, HR-pQCT-based ITS and μFEA measurements discriminate fracture status in postmenopausal women independent of DXA measurements. Moreover, these results suggest that preferential loss of plate-like trabeculae contribute to lower trabecular bone and whole bone stiffness in women with fractures. We conclude that HR-pQCT-based ITS and μFEA measurements increase our understanding of the microstructural pathogenesis of fragility fracture in postmenopausal women. PMID:22072446

Detail of interior of compressed air chamber showing top of ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

Detail of interior of compressed air chamber showing top of working chamber and tie rods that strengthen the outer shell plates of the compression chamber. - Sub Marine Explorer, Located along the beach of Isla San Telmo, Pearl Islands, Isla San Telmo, Former Panama Canal Zone, CZ

CNGA3 Deficiency Affects Cone Synaptic Terminal Structure and Function and Leads to Secondary Rod Dysfunction and Degeneration

PubMed Central

Xu, Jianhua; Morris, Lynsie M.; Michalakis, Stylianos; Biel, Martin; Fliesler, Steven J.; Sherry, David M.

2012-01-01

Purpose. To investigate rod function and survival after cone dysfunction and degeneration in a mouse model of cone cyclic nucleotide-gated (CNG) channel deficiency. Methods. Rod function and survival in mice with cone CNG channel subunit CNGA3 deficiency (CNGA3−/− mice) were evaluated by electroretinographic (ERG), morphometric, and Western blot analyses. The arrangement, integrity, and ultrastructure of photoreceptor terminals were investigated by immunohistochemistry and electron microscopy. Results. The authors found loss of cone function and cone death accompanied by impairment of rods and rod-driven signaling in CNGA3−/− mice. Scotopic ERG b-wave amplitudes were reduced by 15% at 1 month, 30% at 6 months, and 40% at 9 months and older, while scotopic a-wave amplitudes were decreased by 20% at 9 months, compared with ERGs of age-matched wild-type mice. Outer nuclear layer thickness in CNGA3−/− retina was reduced by 15% at 12 months compared with age-matched wild-type controls. This was accompanied by a 30%–40% reduction in expression of rod-specific proteins, including rhodopsin, rod transducin α-subunit, and glutamic acid-rich protein (GARP). Cone terminals in the CNGA3−/− retina showed a progressive loss of neurochemical and ultrastructural integrity. Abnormalities were observed as early as 1 month. Disorganized rod terminal ultrastructure was noted by 12 months. Conclusions. These findings demonstrate secondary rod impairment and degeneration after cone degeneration in mice with cone CNG channel deficiency. Loss of cone phototransduction accompanies the compromised integrity of cone terminals. With time, rod synaptic structure, function, and viability also become compromised. PMID:22247469

Apparatus and methods for installing, removing and adjusting an inner turbine shell section relative to an outer turbine shell section

DOEpatents

Leach, David; Bergendahl, Peter Allen; Waldo, Stuart Forrest; Smith, Robert Leroy; Phelps, Robert Kim

2001-01-01

A turbine includes upper and lower inner shell sections mounting the nozzles and shrouds and which inner shell is supported by pins secured to a surrounding outer shell. To disassemble the turbine for access to the inner shell sections and rotor, an alignment fixture is secured to the lower outer shell section and has pins engaging the inner shell section. To disassemble the turbine, the inner shell weight is transferred to the lower outer shell section via the alignment fixture and cradle pins. Roller assemblies are inserted through access openings vacated by support pins to permit rotation of the lower inner shell section out of and into the lower outer shell section during disassembly and assembly. The alignment fixture includes adjusting rods for adjusting the inner shell axially, vertically, laterally and about a lateral axis. A roller over-cage is provided to rotate the inner shell and a dummy shell to facilitate assembly and disassembly in the field.

Design and evaluation of a bolted joint for a discrete carbon-epoxy rod-reinforced hat section

NASA Technical Reports Server (NTRS)

Rousseau, Carl Q.; Baker, Donald J.

1996-01-01

The use of prefabricated pultruded carbon-epoxy rods has reduced the manufacturing complexity and costs of stiffened composite panels while increasing the damage tolerance of the panels. However, repairability of these highly efficient discrete stiffeners has been a concern. Design, analysis, and test results are presented in this paper for a bolted-joint repair for the pultruded rod concept that is capable of efficiently transferring axial loads in a hat-section stiffener on the upper skin segment of a heavily loaded aircraft wing component. A tension and a compression joint design were evaluated. The tension joint design achieved approximately 1.0% strain in the carbon-epoxy rod-reinforced hat-section and failed in a metal fitting at 166% of the design ultimate load. The compression joint design failed in the carbon-epoxy rod-reinforced hat-section test specimen area at approximately 0.7% strain and at 110% of the design ultimate load. This strain level of 0.7% in compression is similar to the failure strain observed in previously reported carbon-epoxy rod-reinforced hat-section column tests.

Use of border information in the classification of mammographic masses

NASA Astrophysics Data System (ADS)

Varela, C.; Timp, S.; Karssemeijer, N.

2006-01-01

We are developing a new method to characterize the margin of a mammographic mass lesion to improve the classification of benign and malignant masses. Towards this goal, we designed features that measure the degree of sharpness and microlobulation of mass margins. We calculated these features in a border region of the mass defined as a thin band along the mass contour. The importance of these features in the classification of benign and malignant masses was studied in relation to existing features used for mammographic mass detection. Features were divided into three groups, each representing a different mass segment: the interior region of a mass, the border and the outer area. The interior and the outer area of a mass were characterized using contrast and spiculation measures. Classification was done in two steps. First, features representing each of the three mass segments were merged into a neural network classifier resulting in a single regional classification score for each segment. Secondly, a classifier combined the three single scores into a final output to discriminate between benign and malignant lesions. We compared the classification performance of each regional classifier and the combined classifier on a data set of 1076 biopsy proved masses (590 malignant and 486 benign) from 481 women included in the Digital Database for Screening Mammography. Receiver operating characteristic (ROC) analysis was used to evaluate the accuracy of the classifiers. The area under the ROC curve (Az) was 0.69 for the interior mass segment, 0.76 for the border segment and 0.75 for the outer mass segment. The performance of the combined classifier was 0.81 for image-based and 0.83 for case-based evaluation. These results show that the combination of information from different mass segments is an effective approach for computer-aided characterization of mammographic masses. An advantage of this approach is that it allows the assessment of the contribution of regions rather than individual features. Results suggest that the border and the outer areas contained the most valuable information for discrimination between benign and malignant masses.

FUEL ELEMENT FOR NUCLEAR REACTORS

DOEpatents

Bassett, C.H.

1961-11-21

A fuel element is designed which is particularly adapted for reactors of high power density used to generate steam for the production of electricity. The fuel element consists of inner and outer concentric tubes forming an annular chamber within which is contained fissionable fuel pellet segments, wedge members interposed between the fuel segments, and a spring which, acting with wedge members, urges said fuel pellets radially into contact against the inner surface of the outer tube. The wedge members may be a fertile material convertible into fissionable fuel material by absorbing neutrons emitted from the fissionable fuel pellet segments. The costly grinding of cylindrical fuel pellets to close tolerances for snug engagement is reduced because the need to finish the exact size is eliminated. (AEC)

Guiding and amplification properties of rod-type photonic crystal fibers with sectioned core doping

NASA Astrophysics Data System (ADS)

Selleri, S.; Poli, F.; Passaro, D.; Cucinotta, A.; Lægsgaard, J.; Broeng, J.

2009-05-01

Rod-type photonic crystal fibers are large mode area double-cladding fibers with an outer diameter of few millimeters which can provide important advantages for high-power lasers and amplifiers. Numerical studies have recently demonstrated the guidance of higher-order modes in these fibers, which can worsen the output beam quality of lasers and amplifiers. In the present analysis a sectioned core doping has been proposed for Ybdoped rod-type photonic crystal fibers, with the aim to improve the higher-order mode suppression. A full-vector modal solver based on the finite element method has been applied to properly design the low refractive index ring in the fiber core, which can provide an increase of the differential overlap between the fundamental and the higher-order mode. Then, the gain competition among the guided modes along the Yb-doped rod-type fibers has been investigated with a spatial and spectral amplifier model. Simulation results have shown the effectiveness of the sectioned core doping in worsening the higher-order mode overlap on the doped area, thus providing an effective single-mode behavior of the Yb-doped rod-type photonic crystal fibers.

Bcl-xL-mediated remodeling of rod and cone synaptic mitochondria after postnatal lead exposure: electron microscopy, tomography and oxygen consumption.

PubMed

Perkins, Guy A; Scott, Ray; Perez, Alex; Ellisman, Mark H; Johnson, Jerry E; Fox, Donald A

2012-01-01

Postnatal lead exposure produces rod-selective and Bax-mediated apoptosis, decreased scotopic electroretinograms (ERGs), and scotopic and mesopic vision deficits in humans and/or experimental animals. Rod, but not cone, inner segment mitochondria were considered the primary site of action. However, photoreceptor synaptic mitochondria were not examined. Thus, our experiments investigated the structural and functional effects of environmentally relevant postnatal lead exposure on rod spherule and cone pedicle mitochondria and whether Bcl-xL overexpression provided neuroprotection. C57BL/6N mice pups were exposed to lead only during lactation via dams drinking water containing lead acetate. The blood [Pb] at weaning was 20.6±4.7 µg/dl, which decreased to the control value by 2 months. To assess synaptic mitochondrial structural differences and vulnerability to lead exposure, wild-type and transgenic mice overexpressing Bcl-xL in photoreceptors were used. Electron microscopy, three-dimensional electron tomography, and retinal and photoreceptor synaptic terminal oxygen consumption (QO(2)) studies were conducted in adult control, Bcl-xL, lead, and Bcl-xL/lead mice. The spherule and pedicle mitochondria in lead-treated mice were swollen, and the cristae structure was markedly changed. In the lead-treated mice, the mitochondrial cristae surface area and volume (abundance: measure correlated with ATP (ATP) synthesis) were decreased in the spherules and increased in the pedicles. Pedicles also had an increased number of crista segments per volume. In the lead-treated mice, the number of segments/crista and fraction of cristae with multiple segments (branching) similarly increased in spherule and pedicle mitochondria. Lead-induced remodeling of spherule mitochondria produced smaller cristae with more branching, whereas pedicle mitochondria had larger cristae with more branching and increased crista junction (CJ) diameter. Lead decreased dark- and light-adapted photoreceptor and dark-adapted photoreceptor synaptic terminal QO(2). Bcl-xL partially blocked many of the lead-induced alterations relative to controls. However, spherules still had partially decreased abundance, whereas pedicles still had increased branching, increased crista segments per volume, and increased crista junction diameter. Moreover, photoreceptor and synaptic QO(2) were only partially recovered. These findings reveal cellular and compartmental specific differences in the structure and vulnerability of rod and cone inner segment and synaptic mitochondria to postnatal lead exposure. Spherule and pedicle mitochondria in lead-exposed mice displayed complex and distinguishing patterns of cristae and matrix damage and remodeling consistent with studies showing that synaptic mitochondria are more sensitive to Ca(2+) overload, oxidative stress, and ATP loss than non-synaptic mitochondria. The lead-induced decreases in QO(2) likely resulted from the decreased spherule cristae abundance and smaller cristae, perhaps due to Bax-mediated effects as they occurred in apoptotic rod inner segments. The increase in pedicle cristae abundance and CJ diameter could have resulted from increased Drp1-mediated fission, as small mitochondrial fragments were observed. The mechanisms of Bcl-xL-mediated remodeling might occur via interaction with formation of CJ protein 1 (Fcj1), whereas the partial protection of synaptic QO(2) might result from the enhanced efficiency of energy metabolism via Bcl-xL's direct interaction with the F1F0 ATP synthase and/or regulation of cellular redox status. These lead-induced alterations in photoreceptor synaptic terminal mitochondria likely underlie the persistent scotopic and mesopic deficits in lead-exposed children, workers, and experimental animals. Our findings stress the clinical and scientific importance of examining synaptic dysfunction following injury or disease during development, and developing therapeutic treatments that prevent synaptic degeneration in retinal and neurodegenerative disorders even when apoptosis is blocked.

Photoreceptor Cells With Profound Structural Deficits Can Support Useful Vision in Mice

PubMed Central

Thompson, Stewart; Blodi, Frederick R.; Lee, Swan; Welder, Chris R.; Mullins, Robert F.; Tucker, Budd A.; Stasheff, Steven F.; Stone, Edwin M.

2014-01-01

Purpose. In animal models of degenerative photoreceptor disease, there has been some success in restoring photoreception by transplanting stem cell–derived photoreceptor cells into the subretinal space. However, only a small proportion of transplanted cells develop extended outer segments, considered critical for photoreceptor cell function. The purpose of this study was to determine whether photoreceptor cells that lack a fully formed outer segment could usefully contribute to vision. Methods. Retinal and visual function was tested in wild-type and Rds mice at 90 days of age (RdsP90). Photoreceptor cells of mice homozygous for the Rds mutation in peripherin 2 never develop a fully formed outer segment. The electroretinogram and multielectrode recording of retinal ganglion cells were used to test retinal responses to light. Three distinct visual behaviors were used to assess visual capabilities: the optokinetic tracking response, the discrimination-based visual water task, and a measure of the effect of vision on wheel running. Results. RdsP90 mice had reduced but measurable electroretinogram responses to light, and exhibited light-evoked responses in multiple types of retinal ganglion cells, the output neurons of the retina. In optokinetic and discrimination-based tests, acuity was measurable but reduced, most notably when contrast was decreased. The wheel running test showed that RdsP90 mice needed 3 log units brighter luminance than wild type to support useful vision (10 cd/m2). Conclusions. Photoreceptors that lack fully formed outer segments can support useful vision. This challenges the idea that normal cellular structure needs to be completely reproduced for transplanted cells to contribute to useful vision. PMID:24569582

Neutronic reactor

DOEpatents

Wende, Charles W. J.

1976-08-17

A safety rod for a nuclear reactor has an inner end portion having a gamma absorption coefficient and neutron capture cross section approximately equal to those of the adjacent shield, a central portion containing materials of high neutron capture cross section and an outer end portion having a gamma absorption coefficient at least equal to that of the adjacent shield.

76 FR 19122 - Record of Decision (ROD) for Authorizing the Use of Outer Continental Shelf (OCS) Sand Resources...

Federal Register 2010, 2011, 2012, 2013, 2014

2011-04-06

... Aeronautics and Space Administration's Wallops Flight Facility Shoreline Restoration and Infrastructure... authorize the use of OCS sand resources in National Aeronautics and Space Administration's (NASA's) Wallops... infrastructure on the WFF (such as rocket launch pads, runways, and launch control centers) valued at over $1...

Tool and Method for Testing the Resistance of the Snow Road Cover to Destruction

NASA Astrophysics Data System (ADS)

Zhelykevich, R.; Lysyannikov, A.; Kaiser, Yu; Serebrenikova, Yu; Lysyannikova, N.; Shram, V.; Kravtsova, Ye; Plakhotnikova, M.

2016-06-01

The paper presents the design of the tool for efficient determination of the hardness of the snow road coating. The tool increases vertical positioning of the rod with the tip through replacement of the rod slide friction of the ball element by roll friction of its outer bearing race in order to enhance the accuracy of determining the hardness of the snow-ice road covering. A special feature of the tool consists in possibility of creating different impact energy by the change of the lifting height of the rod with the tip (indenter) and the exchangeable load mass. This allows the study of the influence of the tip shape and the impact energy on the snow strength parameters in a wide range, extends the scope of application of the durometer and makes possible to determine the strength of snow-ice formations by indenters with various geometrical parameters depending on climatic conditions.

Pathology in a tube step 2: simple rapid fabrication of curved circular cross section millifluidic channels for biopsy preparation/3D imaging towards pancreatic cancer detection and diagnosis

NASA Astrophysics Data System (ADS)

Das, Ronnie; Burfeind, Chris W.; Lim, Saniel D.; Patle, Shubham; Seibel, Eric J.

2018-02-01

3D pathology is intrinsically dependent on 3D microscopy, or the whole tissue imaging of patient tissue biopsies (TBs). Consequently, unsectioned needle specimens must be processed whole: a procedure which cannot necessarily be accomplished through manual methods, or by retasking automated pathology machines. Thus "millifluidic" devices (for millimeter-scale biopsies) are an ideal solution for tissue handling/preparation. TBs are large, messy and a solid-liquid mixture; they vary in material, geometry and structure based on the organ biopsied, the clinician skill and the needle type used. As a result, traditional microfluidic devices are insufficient to handle such mm-sized samples and their associated fabrication techniques are impractical and costly with respect to time/efficiency. Our research group has devised a simple, rapid fabrication process for millifluidic devices using jointed skeletal molds composed of machined, reusable metal rods, segmented rods and stranded wire as structural cores; these cores are surrounded by Teflon outer housing. We can therefore produce curving, circular-cross-section (CCCS) millifluidic channels in rapid fashion that cannot normally be achieved by microfabrication, micro-/CNC-machining, or 3D printing. The approach has several advantages. CLINICAL: round channels interface coring needles. PROCESSING: CCCS channels permit multi-layer device designs for additional (processing, monitoring, testing) stages. REUSABILITY: for a biopsy/needle diameter, molding (interchangeable) components may be produced one-time then reused for other designs. RAPID: structural cores can be quickly removed due to Teflon®'s ultra-low friction; housing may be released with ethanol; PDMS volumes cure faster since metal skeleton molds conduct additional heat from within the curing elastomer.

Cone-like rhodopsin expressed in the all-cone retina of the colubrid pine snake as a potential adaptation to diurnality.

PubMed

Bhattacharyya, Nihar; Darren, Benedict; Schott, Ryan K; Tropepe, Vincent; Chang, Belinda S W

2017-07-01

Colubridae is the largest and most diverse family of snakes, with visual systems that reflect this diversity, encompassing a variety of retinal photoreceptor organizations. The transmutation theory proposed by Walls postulates that photoreceptors could evolutionarily transition between cell types in squamates, but few studies have tested this theory. Recently, evidence for transmutation and rod-like machinery in an all-cone retina has been identified in a diurnal garter snake ( Thamnophis ), and it appears that the rhodopsin gene at least may be widespread among colubrid snakes. However, functional evidence supporting transmutation beyond the existence of the rhodopsin gene remains rare. We examined the all-cone retina of another colubrid, Pituophis melanoleucus , thought to be more secretive/burrowing than Thamnophis We found that P. melanoleucus expresses two cone opsins (SWS1, LWS) and rhodopsin (RH1) within the eye. Immunohistochemistry localized rhodopsin to the outer segment of photoreceptors in the all-cone retina of the snake and all opsin genes produced functional visual pigments when expressed in vitro Consistent with other studies, we found that P. melanoleucus rhodopsin is extremely blue-shifted. Surprisingly, P. melanoleucus rhodopsin reacted with hydroxylamine, a typical cone opsin characteristic. These results support the idea that the rhodopsin-containing photoreceptors of P. melanoleucus are the products of evolutionary transmutation from rod ancestors, and suggest that this phenomenon may be widespread in colubrid snakes. We hypothesize that transmutation may be an adaptation for diurnal, brighter-light vision, which could result in increased spectral sensitivity and chromatic discrimination with the potential for colour vision. © 2017. Published by The Company of Biologists Ltd.

DEVICE FOR TREATING MATERIALS

DOEpatents

Ohlinger, L.A.; Seitz, F.; Young, G.J.

1959-02-17

Test-hole construction in a reactor to facilitate inserting and removing test specimens from the reactor for irradiation therein is discussed. An elongated chamber extends from the outer face of the reactor shield into the reactor. A shield box, having an open end, is sealed to thc outer face of the reactor shield by its open end surrounding the outer end of the chamber. A removable door is provided in the side wall of the shield box for inscrtion and removal of test specimens. A means operable from thc exterior of the shield box is provided for transferring test specimens between the shield box and the irradiation position within the chamber and consists of an elongated rod having a specimen tray engaging member on its inner end, which may be manipulated by the operator.

Structural Basis for Interactions Between Contactin Family Members and Protein-tyrosine Phosphatase Receptor Type G in Neural Tissues

DOE PAGES

Nikolaienko, Roman M.; Hammel, Michal; Dubreuil, Véronique; ...

2016-08-18

Protein-tyrosine phosphatase receptor type G (RPTPγ/PTPRG) interacts in vitro with contactin-3-6 (CNTN3-6), a group of glycophosphatidylinositol-anchored cell adhesion molecules involved in the wiring of the nervous system. In addition to PTPRG, CNTNs associate with multiple transmembrane proteins and signal inside the cell via cis-binding partners to alleviate the absence of an intracellular region. Here, we use comprehensive biochemical and structural analyses to demonstrate that PTPRG·CNTN3-6 complexes share similar binding affinities and a conserved arrangement. Furthermore, as a first step to identifying PTPRG·CNTN complexes in vivo, we found that PTPRG and CNTN3 associate in the outer segments of mouse rod photoreceptormore » cells. In particular, PTPRG and CNTN3 form cis-complexes at the surface of photoreceptors yet interact in trans when expressed on the surfaces of apposing cells. Further structural analyses suggest that all CNTN ectodomains adopt a bent conformation and might lie parallel to the cell surface to accommodate these cis and trans binding modes. Taken together, these studies identify a PTPRG·CNTN complex in vivo and provide novel insights into PTPRG- and CNTN-mediated signaling.« less

Fundamental studies in the molecular basis of laser-induced retinal damage. Annual report, September 1981-August 1982

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lewis

1982-09-01

This research led to new insights in the fundamental mechanisms involved in laser induced retinal damage and some of the fundamental work on these mechanisms lead to new and exciting avenues in the development of rapidly adjustable molecular light filters with important new possibilities for pulsed-laser eye protection. This report summarizes the significant progress of the past year: (1) Development and Fundamental Mechanism of a Rapidly Adjustable Molecular Filter for Pulsed Laser Eye Protection - this research direction resulted from our investigations on cones of the red-eared swamp turtle, Pseudemys scripta elegans. (2) The Optical Density of Turtle Oil Dropletmore » Solutions - it is important both from a practical and fundamental point of view to determine the optical density of turtle oil-droplet suspensions. In view of the high optical densities in this system, tunable-laser resonance Raman spectroscopy, which is the only technique that has been able to provide high-resolution data, is the only technique that is potentially able to obtain the information. (3) Laser-Induced Molecular Alterations in Turtle Retina. (4) Light Driven Enzymatic Reactions in Photoreceptors. (5) Molecular Cytology of Rod Outer Segments.« less

Effect of docosahexaenoic acid and ascorbate on peroxidation of retinal membranes of ODS rats.

PubMed

Wang, Jin-Ye; Sekine, Seiji; Saito, Morio

2003-04-01

Mutant male osteogenic disorder Shionogi (ODS) rats, unable to synthesize ascorbic acid, were fed diets containing a high content of docosahexaenoic acid (DHA) and different amounts of ascorbic acid, to study the effect of DHA on peroxidative susceptibility of the retina and possible antioxidant action of ascorbic acid. ODS rats were fed from 7 weeks of age with diets containing high DHA (6.4% of total energy). A control group received a diet high in linoleic acid. The diets also contained varying amounts of ascorbic acid. Fatty acid compositions and phospholipid hydroperoxides in rod outer segment (ROS) membranes, and retinal ascorbic acid were analyzed. DHA in ROS membranes was significantly increased in rats fed high DHA, compared with the linoleic acid diet. Levels of phospholipid hydroperoxides in the DHA-fed rats were significantly higher than the linoleic acid-fed rats. Ascorbic acid supplementation did not suppress the phospholipid hydroperoxide levels after a high DHA diet, even when the supplement increased the content of retinal ascorbic acid. In conclusion, high DHA feeding induced a marked increase of phospholipid hydroperoxides in ROS membranes of ODS rats. Supplementation of ascorbic acid did not reverse this increase.

Expression of heat shock protein in the atrophic corneal epithelium of the Royal College of Surgeons dystrophic rat.

PubMed

Yamaguchi, K; Yamaguchi, K; Sheedlo, H J; Turner, J E

1991-03-01

We report atrophic changes in the corneal epithelium of Royal College of Surgeons (RCS) dystrophic rats. The thickness of the corneal epithelium of 180-day-old RCS dystrophic rats was significantly decreased compared to that of 26-day-old RCS dystrophic and age-matched Sprague-Dawley (SD) rats. Immunostaining for (Na+ + K+) ATPase in the corneal epithelium of 180-day-old RCS dystrophic rats was dramatically reduced when compared to that of 26-day-old RCS dystrophic and age-matched SD rats. In contrast, heat shock protein immunostaining in the corneal epithelium was dense in all of the basal cells, wing cells, and superficial cells of 180-day-old RCS dystrophic rats but was minimally observed in some of the basal cells and in fewer wing and superficial cells of the corneal epithelium of 26-day-old RCS dystrophic and age-matched SD rats. We speculate that toxic products from the degenerating rod outer segments in the course of retinal dystrophy may affect the corneal epithelium, resulting in its atrophy. It is also possible that heat shock proteins appear in the atrophic corneal epithelium due to its degenerative condition.

Differential distribution of fibroblast growth factor receptors (FGFRs) on foveal cones: FGFR-4 is an early marker of cone photoreceptors.

PubMed

Cornish, Elisa E; Natoli, Riccardo C; Hendrickson, Anita; Provis, Jan M

2004-01-08

Relatively little is known of the expression and distribution of FGF receptors (FGFR) in the primate retina. We investigated expression of FGFRs in developing and adult Macaca monkey retina, paying particular attention to the cone rich, macular region. One fetal human retina was used for diagnostic PCR using primers designed for FGFR1, FGFR2, FGFR3, FGFR4, and FGFR like-protein 1 (FGFrl1) and for probe design to FGFR3, FGFR4, and FGFrl1. Rat cDNA was used to synthesize probes for FGFR1 and FGFR2 with 90% and 93% homology to human, respectively. Paraffin sections of retina from macaque fetuses sacrificed at fetal days (Fd) 64, 73, 85, 105, 115, 120, and 165, and postnatal ages 2.5 and 11 years were used to detect FGF receptors by immunohistochemistry and in situ hybridization. PCR showed each of the FGF receptors are expressed in fetal human retina. In situ hybridization indicated that mRNA for each receptor is expressed in all retinal cell layers during development, but most intensely in the ganglion cell layer (GCL). FGFR2 mRNA is reduced in the adult inner (INL) and outer (ONL) nuclear layers, while FGFrl1 mRNA is virtually absent from the adult ONL. FGFR4 mRNA is particularly intense in fetal and adult cone photoreceptors. Immunoreactivity to FGFR1-FGFR4 was detected in the interphotoreceptor matrix in what appeared to be RPE microvilli associated with developing photoreceptor outer segments, and generally is high in the GCL and low in the INL. Different patterns of FGFR3 and FGFR4 immunoreactivities in the outer plexiform layer (OPL) suggest localization of FGFR3 to horizontal cell processes, with FGFR4 being expressed by both horizontal and bipolar cell processes. FGFR1, FGFR3, and FGFR4 immunoreactivities are present in the inner segments and somata of adult cones. The pedicles of developing and adult cones are FGFR1 and FGFR3 immunoreactive, and the basal, synaptic region is FGFR4 immunoreactive. FGFR4 labels cones almost in their entirety from early in development and is not detected in rods. The fibers of Henle are intensely FGFR4 immunoreactive in adult cones. The results show high levels of FGF receptor expression in developing and adult retina. Differential distribution of FGF receptors across developing and adult photoreceptors suggests specific roles for FGF signalling in development and maintenance of photoreceptors, particularly the specialized cones of the fovea.

Distributed parameter statics of magnetic catheters.

PubMed

Tunay, Ilker

2011-01-01

We discuss how to use special Cosserat rod theory for deriving distributed-parameter static equilibrium equations of magnetic catheters. These medical devices are used for minimally-invasive diagnostic and therapeutic procedures and can be operated remotely or controlled by automated algorithms. The magnetic material can be lumped in rigid segments or distributed in flexible segments. The position vector of the cross-section centroid and quaternion representation of an orthonormal triad are selected as DOF. The strain energy for transversely isotropic, hyperelastic rods is augmented with the mechanical potential energy of the magnetic field and a penalty term to enforce the quaternion unity constraint. Numerical solution is found by 1D finite elements. Material properties of polymer tubes in extension, bending and twist are determined by mechanical and magnetic experiments. Software experiments with commercial FEM software indicate that the computational effort with the proposed method is at least one order of magnitude less than standard 3D FEM.

Electronic properties and reactivity of Pt-doped carbon nanotubes.

PubMed

Tian, Wei Quan; Liu, Lei Vincent; Wang, Yan Alexander

2006-08-14

The structures of the (5,5) single-walled carbon nanotube (SWCNT) segments with hemispheric carbon cages capped at the ends (SWCNT rod) and the Pt-doped SWCNT rods have been studied within density functional theory. Our theoretical studies find that the hemispheric cages introduce localized states on the caps. The cap-Pt-doped SWCNT rods can be utilized as sensors because of the sensitivity of the doped Pt atom. The Pt-doped SWCNT rods can also be used as catalysts, where the doped Pt atom serves as the enhanced and localized active center on the SWCNT. The adsorptions of C(2)H(4) and H(2) on the Pt atom in the Pt-doped SWCNT rods reveal different adsorption characteristics. The adsorption of C(2)H(4) on the Pt atom in all of the three Pt-doped SWCNT rods studied (cap-end-doped, cap-doped, and wall-doped) is physisorption with the strongest interaction occurring in the middle of the sidewall of the SWCNT. On the other hand, the adsorption of H(2) on the Pt atom at the sidewall of the SWCNT is chemisorption resulting in the decomposition of H(2), and the adsorption of H(2) at the hemispheric caps is physisorption.

Design and Evaluation of a Bolted Joint for a Discrete Carbon-Epoxy Rod-Reinforced Hat Section

NASA Technical Reports Server (NTRS)

Baker, Donald J.; Rousseau, Carl Q.

1996-01-01

The use of pre-fabricated pultruded carbon-epoxy rods has reduced the manufacturing complexity and costs of stiffened composite panels while increasing the damage tolerance of the panels. However, repairability of these highly efficient discrete stiffeners has been a concern. Design, analysis, and test results are presented in this paper for a bolted-joint repair for the pultruded rod concept that is capable of efficiently transferring axial loads in a hat-section stiffener on the upper skin segment of a heavily loaded aircraft wing component. A tension and a compression joint design were evaluated. The tension joint design achieved approximately 1.0 percent strain in the carbon-epoxy rod-reinforced hat-section and failed in a metal fitting at 166 percent of the design ultimate load. The compression joint design failed in the carbon-epoxy rod-reinforced hat-section test specimen area at approximately 0.7 percent strain and at 110 percent of the design ultimate load. This strain level of 0.7 percent in compression is similar to the failure strain observed in previously reported carbon-epoxy rod-reinforced hat-section column tests.

Restoration of outer segments of foveal photoreceptors after resolution of central serous chorioretinopathy.

PubMed

Ojima, Yumiko; Tsujikawa, Akitaka; Yamashiro, Kenji; Ooto, Sotaro; Tamura, Hiroshi; Yoshimura, Nagahisa

2010-01-01

To study morphologically and functionally the prognosis of damaged outer segments of the foveal photoreceptor layer in eyes with resolved central serous chorioretinopathy (CSC). We studied retrospectively the medical records of 70 patients (74 eyes) with resolved CSC. Optical coherence tomography was used to detect the junctions between inner and outer segments of the photoreceptors (IS/OS) as a hallmark of the integrity of the outer photoreceptor layer. In 53 eyes (71.6%), the IS/OS line was clearly detected beneath the fovea immediately after resolution of the retinal detachment, with good visual acuity (VA). In the remaining 21 eyes (28.4%), however, the foveal IS/OS line could not be detected shortly after resolution of CSC, and VA was variable, ranging from 0.1 to 1.5 (median, 0.9). Of these 21 eyes, 15 had a follow-up examination with OCT, and in four the foveal IS/OS line was not detected at the follow-up and vision in these eyes remained poor. However, nine eyes showed recovery of the foveal IS/OS line during follow-up, and these eyes had substantial visual recovery. Immediately after resolution of active CSC, although the IS/OS line cannot be detected beneath the fovea, it often shows restoration over time, with visual recovery, though in some eyes no restoration takes place and the prognosis remains poor.

Modeling the Role of Incisures in Vertebrate Phototransduction

PubMed Central

Caruso, Giovanni; Bisegna, Paolo; Shen, Lixin; Andreucci, Daniele; Hamm, Heidi E.; DiBenedetto, Emmanuele

2006-01-01

Phototransduction is mediated by a G-protein-coupled receptor-mediated cascade, activated by light and localized to rod outer segment (ROS) disk membranes, which, in turn, drives a diffusion process of the second messengers cGMP and Ca2+ in the ROS cytosol. This process is hindered by disks—which, however, bear physical cracks, known as incisures, believed to favor the longitudinal diffusion of cGMP and Ca2+. This article is aimed at highlighting the biophysical functional role and significance of incisures, and their effect on the local and global response of the photocurrent. Previous work on this topic regarded the ROS as well stirred in the radial variables, lumped the diffusion mechanism on the longitudinal axis of the ROS, and replaced the cytosolic diffusion coefficients by effective ones, accounting for incisures through their total patent area only. The fully spatially resolved model recently published by our group is a natural tool to take into account other significant details of incisures, including their geometry and distribution. Using mathematical theories of homogenization and concentrated capacity, it is shown here that the complex diffusion process undergone by the second messengers cGMP and Ca2+ in the ROS bearing incisures can be modeled by a family of two-dimensional diffusion processes on the ROS cross sections, glued together by other two-dimensional diffusion processes, accounting for diffusion in the ROS outer shell and in the bladelike regions comprised by the stack of incisures. Based on this mathematical model, a code has been written, capable of incorporating an arbitrary number of incisures and activation sites, with any given arbitrary distribution within the ROS. The code is aimed at being an operational tool to perform numerical experiments of phototransduction, in rods with incisures of different geometry and structure, under a wide spectrum of operating conditions. The simulation results show that incisures have a dual biophysical function. On the one hand, since incisures line up from disk to disk, they create vertical cytoplasmic channels crossing the disks, thus facilitating diffusion of second messengers; on the other hand, at least in those species bearing multiple incisures, they divide the disks into lobes like the petals of a flower, thus confining the diffusion of activated phosphodiesterase and localizing the photon response. Accordingly, not only the total area of incisures, but their geometrical shape and distribution as well, significantly influence the global photoresponse. PMID:16714347

Loss of ift122, a Retrograde Intraflagellar Transport (IFT) Complex Component, Leads to Slow, Progressive Photoreceptor Degeneration Due to Inefficient Opsin Transport.

PubMed

Boubakri, Meriam; Chaya, Taro; Hirata, Hiromi; Kajimura, Naoko; Kuwahara, Ryusuke; Ueno, Akiko; Malicki, Jarema; Furukawa, Takahisa; Omori, Yoshihiro

2016-11-18

In the retina, aberrant opsin transport from cell bodies to outer segments leads to retinal degenerative diseases such as retinitis pigmentosa. Opsin transport is facilitated by the intraflagellar transport (IFT) system that mediates the bidirectional movement of proteins within cilia. In contrast to functions of the anterograde transport executed by IFT complex B (IFT-B), the precise functions of the retrograde transport mediated by IFT complex A (IFT-A) have not been well studied in photoreceptor cilia. Here, we analyzed developing zebrafish larvae carrying a null mutation in ift122 encoding a component of IFT-A. ift122 mutant larvae show unexpectedly mild phenotypes, compared with those of mutants defective in IFT-B. ift122 mutants exhibit a slow onset of progressive photoreceptor degeneration mainly after 7 days post-fertilization. ift122 mutant larvae also develop cystic kidney but not curly body, both of which are typically observed in various ciliary mutants. ift122 mutants display a loss of cilia in the inner ear hair cells and nasal pit epithelia. Loss of ift122 causes disorganization of outer segment discs. Ectopic accumulation of an IFT-B component, ift88, is observed in the ift122 mutant photoreceptor cilia. In addition, pulse-chase experiments using GFP-opsin fusion proteins revealed that ift122 is required for the efficient transport of opsin and the distal elongation of outer segments. These results show that IFT-A is essential for the efficient transport of outer segment proteins, including opsin, and for the survival of retinal photoreceptor cells, rendering the ift122 mutant a unique model for human retinal degenerative diseases. © 2016 by The American Society for Biochemistry and Molecular Biology, Inc.

Loss of ift122, a Retrograde Intraflagellar Transport (IFT) Complex Component, Leads to Slow, Progressive Photoreceptor Degeneration Due to Inefficient Opsin Transport*

PubMed Central

Boubakri, Meriam; Chaya, Taro; Hirata, Hiromi; Kajimura, Naoko; Kuwahara, Ryusuke; Ueno, Akiko; Malicki, Jarema; Furukawa, Takahisa; Omori, Yoshihiro

2016-01-01

In the retina, aberrant opsin transport from cell bodies to outer segments leads to retinal degenerative diseases such as retinitis pigmentosa. Opsin transport is facilitated by the intraflagellar transport (IFT) system that mediates the bidirectional movement of proteins within cilia. In contrast to functions of the anterograde transport executed by IFT complex B (IFT-B), the precise functions of the retrograde transport mediated by IFT complex A (IFT-A) have not been well studied in photoreceptor cilia. Here, we analyzed developing zebrafish larvae carrying a null mutation in ift122 encoding a component of IFT-A. ift122 mutant larvae show unexpectedly mild phenotypes, compared with those of mutants defective in IFT-B. ift122 mutants exhibit a slow onset of progressive photoreceptor degeneration mainly after 7 days post-fertilization. ift122 mutant larvae also develop cystic kidney but not curly body, both of which are typically observed in various ciliary mutants. ift122 mutants display a loss of cilia in the inner ear hair cells and nasal pit epithelia. Loss of ift122 causes disorganization of outer segment discs. Ectopic accumulation of an IFT-B component, ift88, is observed in the ift122 mutant photoreceptor cilia. In addition, pulse-chase experiments using GFP-opsin fusion proteins revealed that ift122 is required for the efficient transport of opsin and the distal elongation of outer segments. These results show that IFT-A is essential for the efficient transport of outer segment proteins, including opsin, and for the survival of retinal photoreceptor cells, rendering the ift122 mutant a unique model for human retinal degenerative diseases. PMID:27681595

Melanopsin is required for non-image-forming photic responses in blind mice.

PubMed

Panda, Satchidananda; Provencio, Ignacio; Tu, Daniel C; Pires, Susana S; Rollag, Mark D; Castrucci, Ana Maria; Pletcher, Mathew T; Sato, Trey K; Wiltshire, Tim; Andahazy, Mary; Kay, Steve A; Van Gelder, Russell N; Hogenesch, John B

2003-07-25

Although mice lacking rod and cone photoreceptors are blind, they retain many eye-mediated responses to light, possibly through photosensitive retinal ganglion cells. These cells express melanopsin, a photopigment that confers this photosensitivity. Mice lacking melanopsin still retain nonvisual photoreception, suggesting that rods and cones could operate in this capacity. We observed that mice with both outer-retinal degeneration and a deficiency in melanopsin exhibited complete loss of photoentrainment of the circadian oscillator, pupillary light responses, photic suppression of arylalkylamine-N-acetyltransferase transcript, and acute suppression of locomotor activity by light. This indicates the importance of both nonvisual and classical visual photoreceptor systems for nonvisual photic responses in mammals.

Steam generator support system

DOEpatents

Moldenhauer, J.E.

1987-08-25

A support system for connection to an outer surface of a J-shaped steam generator for use with a nuclear reactor or other liquid metal cooled power source is disclosed. The J-shaped steam generator is mounted with the bent portion at the bottom. An arrangement of elongated rod members provides both horizontal and vertical support for the steam generator. The rod members are interconnected to the steam generator assembly and a support structure in a manner which provides for thermal distortion of the steam generator without the transfer of bending moments to the support structure and in a like manner substantially minimizes forces being transferred between the support structure and the steam generator as a result of seismic disturbances. 4 figs.

Steam generator support system

DOEpatents

Moldenhauer, James E.

1987-01-01

A support system for connection to an outer surface of a J-shaped steam generator for use with a nuclear reactor or other liquid metal cooled power source. The J-shaped steam generator is mounted with the bent portion at the bottom. An arrangement of elongated rod members provides both horizontal and vertical support for the steam generator. The rod members are interconnected to the steam generator assembly and a support structure in a manner which provides for thermal distortion of the steam generator without the transfer of bending moments to the support structure and in a like manner substantially minimizes forces being transferred between the support structure and the steam generator as a result of seismic disturbances.

Posterior Double Vertebral Column Resections Combined with Satellite Rod Technique to Correct Severe Congenital Angular Kyphosis.

PubMed

Sun, Xu; Zhu, Ze-Zhang; Chen, Xi; Liu, Zhen; Wang, Bin; Qiu, Yong

2016-08-01

This paper presents a highly challenging technique involving posterior double vertebral column resections (VCRs) and satellite rods placement. This was a young adult case with severe angular thoracolumbar kyphosis of 101 degrees, secondary to anterior segmentation failure from T11 to L1 . There were hemivertebrae at T11 and T12 , and a wedged vertebra at L1 . He received double VCRs at T12 and T11 and instrumented fusion from T6 to L4 via a posterior only approach. Autologous grafts and a cage were placed between the bony surfaces of the osteotomy gap. Once closure of osteotomy was achieved, bilateral permanent CoCr rods were placed with addition of satellite rods. Postoperative X-ray demonstrated marked correction of kyphosis. On the 10(th) days after surgery, the patient was able to walk without assistance. In conclusion, double VCRs are effective to correct severe angular kyphosis, and addition of satellite rods may be imperative to enhance instrumentation strength and thus prevent correction loss. © 2016 Chinese Orthopaedic Association and John Wiley & Sons Australia, Ltd.

Dark adaptation in relation to choroidal thickness in healthy young subjects: a cross-sectional, observational study.

PubMed

Munch, Inger Christine; Altuntas, Cigdem; Li, Xiao Qiang; Jackson, Gregory R; Klefter, Oliver Niels; Larsen, Michael

2016-07-11

Dark adaptation is an energy-requiring process in the outer retina nourished by the profusely perfused choroid. We hypothesized that variations in choroidal thickness might affect the rate of dark adaptation. Cross-sectional, observational study of 42 healthy university students (mean age 25 ± 2.0 years, 29 % men) who were examined using an abbreviated automated dark adaptometry protocol with a 2° diameter stimulus centered 5° above the point of fixation. The early, linear part of the rod-mediated dark adaptation curve was analyzed to extract the time required to reach a sensitivity of 5.0 × 10(-3) cd/m2 (time to rod intercept) and the slope (rod adaptation rate). The choroid was imaged using enhanced-depth imaging spectral-domain optical coherence tomography (EDI-OCT). The time to the rod intercept was 7.3 ± 0.94 (range 5.1 - 10.2) min. Choroidal thickness 2.5° above the fovea was 348 ± 104 (range 153-534) μm. There was no significant correlation between any of the two measures of rod-mediated dark adaptation and choroidal thickness (time to rod intercept versus choroidal thickness 0.072 (CI95 -0.23 to 0.38) min/100 μm, P = 0.64, adjusted for age and sex). There was no association between the time-to-rod-intercept or the dark adaptation rate and axial length, refraction, gender or age. Choroidal thickness, refraction and ocular axial length had no detectable effect on rod-mediated dark adaptation in healthy young subjects. Our results do not support that variations in dark adaptation can be attributed to variations in choroidal thickness.

Rod-driven OFF pathway responses in the distal retina: dark-adapted flicker electroretinogram in mouse.

PubMed

Lei, Bo

2012-01-01

The rodent retina does not exhibit a positive OFF-response in the electroretinogram (ERG), which makes it difficult to evaluate its OFF-pathway functions in vivo. We studied the rod-driven OFF pathway responses by using a dark-adapted 10-Hz flicker ERG procedure in mouse. Conventional ERGs and 10-Hz dark-adapted flicker ERGs were obtained in wild-type mice (C57BL/6), in mice with pure rod (cpfl1) or pure cone (rho(-/-)) function, and in nob1 mice which have a selective ON-pathway defect. To isolate the response from ON or OFF pathway, glutamate analogs 2-amino-4-phosphobutyric acid (APB, an ON pathway blocker) and cis-2, 3-piperidine-dicarboxylic acid (PDA, an OFF pathway blocker), were injected intravitreally. The amplitude-intensity profile of the dark-adapted 10-Hz flicker ERG in the wild-type mice exhibits two peaks at middle and high light intensities. The two peaks represent rod- and cone-driven responses respectively. In APB-treated C57BL/6 mice and in nob1 mice, the dark-adapted ERG b-waves were absent. However, both rod- and cone-driven OFF pathway responses were evident with flicker ERG recording. At middle light intensities that activate only rod system, the flicker ERG responses in saline-injected nob1 mice were similar to those in APB-injected cpfl1 mice and wild-type mice. These responses are sensitive to PDA. The amplitudes of these rod-driven OFF pathway responses were approximately 20% of the total rod-driven flicker ERG responses. We demonstrate that the rod-OFF bipolar cell pathway is functional in the outer retina. The dark-adapted flicker ERG is practical for the evaluation of rod- and cone-driven responses, and the residual OFF pathway signals in subjects with ON pathway defects.

DIRECT-CYCLE, BOILING-WATER NUCLEAR REACTOR

DOEpatents

Harrer, J.M.; Fromm, L.W. Jr.; Kolba, V.M.

1962-08-14

A direct-cycle boiling-water nuclear reactor is described that employs a closed vessel and a plurality of fuel assemblies, each comprising an outer tube closed at its lower end, an inner tube, fuel rods in the space between the tubes and within the inner tube. A body of water lying within the pressure vessel and outside the fuel assemblies is converted to saturated steam, which enters each fuel assembly at the top and is converted to superheated steam in the fuel assembly while it is passing therethrough first downward through the space between the inner and outer tubes of the fuel assembly and then upward through the inner tube. (AEC)

Light absorption and plasmon – exciton interaction in three-layer nanorods with a gold core and outer shell composed of molecular J- and H-aggregates of dyes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shapiro, B I; Tyshkunova, E S; Kondorskiy, A D

2015-12-31

Optical properties of hybrid rod-like nanoparticles, consisting of a gold core, an intermediate passive organic layer (spacer) and outer layer of ordered molecular cyanine dye aggregates, are experimentally and theoretically investigated. It is shown that these dyes can form not only ordered J-aggregates but also H-aggregates (differing by the packing angle of dye molecules in an aggregate and having other spectral characteristics) in the outer shell of the hybrid nanostructure. Absorption spectra of synthesised three-layer nanorods are recorded, and their sizes are determined. The optical properties of the composite nanostructures under study are found to differ significantly, depending on themore » type of the molecular aggregate formed in the outer shell. The experimental data are quantitatively explained based on computer simulation using the finite-difference time-domain (FDTD) method, and characteristic features of the plasmon – exciton interaction in the systems under study are revealed. (nanophotonics)« less

Synaptic remodeling generates synchronous oscillations in the degenerated outer mouse retina

PubMed Central

Haq, Wadood; Arango-Gonzalez, Blanca; Zrenner, Eberhart; Euler, Thomas; Schubert, Timm

2014-01-01

During neuronal degenerative diseases, neuronal microcircuits undergo severe structural alterations, leading to remodeling of synaptic connectivity. The functional consequences of such remodeling are mostly unknown. For instance, in mutant rd1 mouse retina, a common model for Retinitis Pigmentosa, rod bipolar cells (RBCs) establish contacts with remnant cone photoreceptors (cones) as a consequence of rod photoreceptor cell death and the resulting lack of presynaptic input. To assess the functional connectivity in the remodeled, light-insensitive outer rd1 retina, we recorded spontaneous population activity in retinal wholemounts using Ca2+ imaging and identified the participating cell types. Focusing on cones, RBCs and horizontal cells (HCs), we found that these cell types display spontaneous oscillatory activity and form synchronously active clusters. Overall activity was modulated by GABAergic inhibition from interneurons such as HCs and/or possibly interplexiform cells. Many of the activity clusters comprised both cones and RBCs. Opposite to what is expected from the intact (wild-type) cone-ON bipolar cell pathway, cone and RBC activity was positively correlated and, at least partially, mediated by glutamate transporters expressed on RBCs. Deletion of gap junctional coupling between cones reduced the number of clusters, indicating that electrical cone coupling plays a crucial role for generating the observed synchronized oscillations. In conclusion, degeneration-induced synaptic remodeling of the rd1 retina results in a complex self-sustained outer retinal oscillatory network, that complements (and potentially modulates) the recently described inner retinal oscillatory network consisting of amacrine, bipolar and ganglion cells. PMID:25249942

Tunable graded rod laser assembly

NASA Technical Reports Server (NTRS)

AuYeung, John C. (Inventor)

1985-01-01

A tunable laser assembly including a pair of radially graded indexed optical segments aligned to focus the laser to form an external resonant cavity with an optical axis, the respective optical segments are retativity moveable along the optical axis and provide a variable et aion gap sufficient to permit variable tuning of the laser wavelength without altering the effective length of the resonant cavity. The gap also include a saturable absorbing material providing a passive mode-locking of the laser.

TIGRESS highly-segmented high-purity germanium clover detector

NASA Astrophysics Data System (ADS)

Scraggs, H. C.; Pearson, C. J.; Hackman, G.; Smith, M. B.; Austin, R. A. E.; Ball, G. C.; Boston, A. J.; Bricault, P.; Chakrawarthy, R. S.; Churchman, R.; Cowan, N.; Cronkhite, G.; Cunningham, E. S.; Drake, T. E.; Finlay, P.; Garrett, P. E.; Grinyer, G. F.; Hyland, B.; Jones, B.; Leslie, J. R.; Martin, J.-P.; Morris, D.; Morton, A. C.; Phillips, A. A.; Sarazin, F.; Schumaker, M. A.; Svensson, C. E.; Valiente-Dobón, J. J.; Waddington, J. C.; Watters, L. M.; Zimmerman, L.

2005-05-01

The TRIUMF-ISAC Gamma-Ray Escape-Suppressed Spectrometer (TIGRESS) will consist of twelve units of four high-purity germanium (HPGe) crystals in a common cryostat. The outer contacts of each crystal will be divided into four quadrants and two lateral segments for a total of eight outer contacts. The performance of a prototype HPGe four-crystal unit has been investigated. Integrated noise spectra for all contacts were measured. Energy resolutions, relative efficiencies for both individual crystals and for the entire unit, and peak-to-total ratios were measured with point-like sources. Position-dependent performance was measured by moving a collimated source across the face of the detector.

Long-Term Efficacy of GMP Grade Xeno-Free hESC-Derived RPE Cells Following Transplantation

PubMed Central

McGill, Trevor J.; Bohana-Kashtan, Osnat; Stoddard, Jonathan W.; Andrews, Michael D.; Pandit, Neelay; Rosenberg-Belmaker, Lior R.; Wiser, Ofer; Matzrafi, Limor; Banin, Eyal; Reubinoff, Benjamin; Netzer, Nir; Irving, Charles

2017-01-01

Purpose Retinal pigment epithelium (RPE) dysfunction underlies the retinal degenerative process in age-related macular degeneration (AMD), and thus RPE cell replacement provides an optimal treatment target. We characterized longitudinally the efficacy of RPE cells derived under xeno-free conditions from clinical and xeno-free grade human embryonic stem cells (OpRegen) following transplantation into the subretinal space of Royal College of Surgeons (RCS) rats. Methods Postnatal (P) day 20 to 25 RCS rats (n = 242) received a single subretinal injection of 25,000 (low)-, 100,000 (mid)-, or 200,000 (high)-dose xeno-free RPE cells. BSS+ (balanced salt solution) (vehicle) and unoperated eyes served as controls. Optomotor tracking (OKT) behavior was used to quantify functional efficacy. Histology and immunohistochemistry were used to evaluate photoreceptor rescue and transplanted cell survival at 60, 100, 150, and 200 days of age. Results OKT was rescued in a dose-dependent manner. Outer nuclear layer (ONL) was significantly thicker in cell-treated eyes than controls up to P150. Transplanted RPE cells were identified in both the subretinal space and integrated into the host RPE monolayer in animals of all age groups, and often contained internalized photoreceptor outer segments. No pathology was observed. Conclusions OpRegen RPE cells survived, rescued visual function, preserved rod and cone photoreceptors long-term in the RCS rat. Thus, these data support the use of OpRegen RPE cells for the treatment of human RPE cell disorders including AMD. Translational Relevance Our novel xeno-free RPE cells minimize concerns of animal derived contaminants while providing a promising prospective therapy to the diseased retina. PMID:28626601

Human Usher 1B/mouse shaker-1: the retinal phenotype discrepancy explained by the presence/absence of myosin VIIA in the photoreceptor cells.

PubMed

el-Amraoui, A; Sahly, I; Picaud, S; Sahel, J; Abitbol, M; Petit, C

1996-08-01

Usher syndrome type 1 (USH1) associates severe congenital deafness, vestibular dysfunction and progressive retinitis pigmentosa leading to blindness. The gene encoding myosin VIIA is responsible for USH1B. Mutations in the murine orthologous gene lead to the shaker-1 phenotype, which manifests cochlear and vestibular dysfunction, without any retinal defect. To address this phenotypic discrepancy, the expression of myosin VIIA in retinal cells was analyzed in human and mouse during embryonic development and adult life. In the human embryo, myosin VIIA was present first in the pigment epithelium cells, and later in these cells as well as in the photoreceptor cells. In the adult human retina, myosin VIIA was present in both cell types. In contrast, in mouse, only pigment epithelium cells expressed the protein throughout development and adult life. Myosin VIIA was also found to be absent in the photoreceptor cells of other rodents (rat and guinea-pig), whereas these cells expressed the protein in amphibians, avians and primates. These observations suggest that retinitis pigmentosa of USH1B results from a primary rod and cone defect. The USH1B/shaker-1 paradigm illustrates a species-specific cell pattern of gene expression as a possible cause for the discrepancy between phenotypes involving defective orthologous genes in man and mouse. Interestingly, in the photoreceptor cells, myosin VIIA is mainly localized in the inner and base of outer segments as well as in the synaptic ending region where it is co-localized with the synaptic vesicles. Therefore, we suggest that myosin VIIA might play a role in the trafficking of ribbon-synaptic vesicle complexes and the renewal processes of the outer photoreceptor disks.

MreB drives de novo rod morphogenesis in Caulobacter crescentus via remodeling of the cell wall.

PubMed

Takacs, Constantin N; Poggio, Sebastian; Charbon, Godefroid; Pucheault, Mathieu; Vollmer, Waldemar; Jacobs-Wagner, Christine

2010-03-01

MreB, the bacterial actin-like cytoskeleton, is required for the rod morphology of many bacterial species. Disruption of MreB function results in loss of rod morphology and cell rounding. Here, we show that the widely used MreB inhibitor A22 causes MreB-independent growth inhibition that varies with the drug concentration, culture medium conditions, and bacterial species tested. MP265, an A22 structural analog, is less toxic than A22 for growth yet equally efficient for disrupting the MreB cytoskeleton. The action of A22 and MP265 is enhanced by basic pH of the culture medium. Using this knowledge and the rapid reversibility of drug action, we examined the restoration of rod shape in lemon-shaped Caulobacter crescentus cells pretreated with MP265 or A22 under nontoxic conditions. We found that reversible restoration of MreB function after drug removal causes extensive morphological changes including a remarkable cell thinning accompanied with elongation, cell branching, and shedding of outer membrane vesicles. We also thoroughly characterized the composition of C. crescentus peptidoglycan by high-performance liquid chromatography and mass spectrometry and showed that MreB disruption and recovery of rod shape following restoration of MreB function are accompanied by considerable changes in composition. Our results provide insight into MreB function in peptidoglycan remodeling and rod shape morphogenesis and suggest that MreB promotes the transglycosylase activity of penicillin-binding proteins.

77 FR 29682 - Gulf of Mexico, Outer Continental Shelf, Central Planning Area, Oil and Gas Lease Sale 216/222

Federal Register 2010, 2011, 2012, 2013, 2014

2012-05-18

... and Gas Lease Sale: 2012 Central Planning Area (CPA) Lease Sale 216/222 Authority: This NOA is... a ROD following the completion of the Final SEIS for CPA Consolidated Lease Sale 216/222, the final... SEIS updates two previous environmental and socioeconomic analyses for CPA Lease Sale 216/222. The GOM...

Analysis of radially cracked ring segments subject to forces and couples

NASA Technical Reports Server (NTRS)

Gross, B.; Srawley, J. E.

1977-01-01

Results of planar boundary collocation analysis are given for ring segment (C-shaped) specimens with radial cracks, subjected to combined forces and couples. Mode I stress intensity factors and crack mouth opening displacements were determined for ratios of outer to inner radius in the range 1.1 to 2.5 and ratios of crack length to segment width in the range 0.1 to 0.8.

Analysis of radially cracked ring segments subject to forces and couples

NASA Technical Reports Server (NTRS)

Gross, B.; Strawley, J. E.

1975-01-01

Results of planar boundary collocation analysis are given for ring segment (C shaped) specimens with radial cracks, subjected to combined forces and couples. Mode I stress intensity factors and crack mouth opening displacements were determined for ratios of outer to inner radius in the range 1.1 to 2.5, and ratios of crack length to segment width in the range 0.1 to 0.8.

Automatic lumen and outer wall segmentation of the carotid artery using deformable three-dimensional models in MR angiography and vessel wall images.

PubMed

van 't Klooster, Ronald; de Koning, Patrick J H; Dehnavi, Reza Alizadeh; Tamsma, Jouke T; de Roos, Albert; Reiber, Johan H C; van der Geest, Rob J

2012-01-01

To develop and validate an automated segmentation technique for the detection of the lumen and outer wall boundaries in MR vessel wall studies of the common carotid artery. A new segmentation method was developed using a three-dimensional (3D) deformable vessel model requiring only one single user interaction by combining 3D MR angiography (MRA) and 2D vessel wall images. This vessel model is a 3D cylindrical Non-Uniform Rational B-Spline (NURBS) surface which can be deformed to fit the underlying image data. Image data of 45 subjects was used to validate the method by comparing manual and automatic segmentations. Vessel wall thickness and volume measurements obtained by both methods were compared. Substantial agreement was observed between manual and automatic segmentation; over 85% of the vessel wall contours were segmented successfully. The interclass correlation was 0.690 for the vessel wall thickness and 0.793 for the vessel wall volume. Compared with manual image analysis, the automated method demonstrated improved interobserver agreement and inter-scan reproducibility. Additionally, the proposed automated image analysis approach was substantially faster. This new automated method can reduce analysis time and enhance reproducibility of the quantification of vessel wall dimensions in clinical studies. Copyright © 2011 Wiley Periodicals, Inc.

A biomechanical investigation of dual growing rods used for fusionless scoliosis correction.

PubMed

Quick, M E; Grant, C A; Adam, C J; Askin, G N; Labrom, R D; Pearcy, M J

2015-01-01

The use of dual growing rods is a fusionless surgical approach to the treatment of early onset scoliosis which aims to harness potential growth and correct spinal deformity. The purpose of this study was to compare the in-vitro biomechanical response of two different dual rod designs under axial rotation loading. Six porcine spines were dissected into seven level thoracolumbar multi-segment units. Each specimen was mounted and tested in a biaxial Instron machine, undergoing nondestructive left and right axial rotation to peak moments of 4 Nm at a constant rotation rate of 8 deg. s(-1). A motion tracking system (Optotrak) measured 3D displacements of individual vertebrae. Each spine was tested in an un-instrumented state first and then with appropriately sized semi-constrained and 'rigid' growing rods in alternating sequence. The range of motion, neutral zone size and stiffness were calculated from the moment-rotation curves and intervertebral range of motion was calculated from Optotrak data. Irrespective of test sequence, rigid rods showed a significant reduction of total rotation across all instrumented levels (with increased stiffness) whilst semi-constrained rods exhibited similar rotational behavior to the un-instrumented spines (P<0.05). An 11.1% and 8.0% increase in stiffness for left and right axial rotation respectively and 14.9% reduction in total range of motion were recorded with dual rigid rods compared with semi-constrained rods. Based on these findings, the Semi-constrained growing rods were shown to not increase axial rotation stiffness compared with un-instrumented spines. This is thought to provide a more physiological environment for the growing spine compared to dual rigid rod constructs. Copyright © 2014 Elsevier Ltd. All rights reserved.

Radio Frequency Trap for Containment of Plasmas in Antimatter Propulsion Systems Using Rotating Wall Electric Fields

NASA Technical Reports Server (NTRS)

Sims, William Herbert, III (Inventor); Martin, James Joseph (Inventor); Lewis, Raymond A. (Inventor)

2003-01-01

A containment apparatus for containing a cloud of charged particles comprises a cylindrical vacuum chamber having a longitudinal axis. Within the vacuum chamber is a containment region. A magnetic field is aligned with the longitudinal axis of the vacuum chamber. The magnetic field is time invariant and uniform in strength over the containment region. An electric field is also aligned with the longitudinal axis of the vacuum chamber and the magnetic field. The electric field is time invariant, and forms a potential well over the containment region. One or more means are disposed around the cloud of particles for inducing a rotating electric field internal to the vacuum chamber. The rotating electric field imparts energy to the charged particles within the containment region and compress the cloud of particles. The means disposed around the outer surface of the vacuum chamber for inducing a rotating electric field are four or more segments forming a segmented ring, the segments conforming to the outer surface of the vacuum chamber. Each of the segments is energized by a separate alternating voltage. The sum of the voltages imposed on each segment establishes the rotating field. When four segments form a ring, the rotating field is obtained by a signal generator applying a sinusoidal signal phase delayed by 90,180 and 270 degrees in sequence to the four segments.

Increasing the efficiency of designing hemming processes by using an element-based metamodel approach

NASA Astrophysics Data System (ADS)

Kaiser, C.; Roll, K.; Volk, W.

2017-09-01

In the automotive industry, the manufacturing of automotive outer panels requires hemming processes in which two sheet metal parts are joined together by bending the flange of the outer part over the inner part. Because of decreasing development times and the steadily growing number of vehicle derivatives, an efficient digital product and process validation is necessary. Commonly used simulations, which are based on the finite element method, demand significant modelling effort, which results in disadvantages especially in the early product development phase. To increase the efficiency of designing hemming processes this paper presents a hemming-specific metamodel approach. The approach includes a part analysis in which the outline of the automotive outer panels is initially split into individual segments. By doing a para-metrization of each of the segments and assigning basic geometric shapes, the outline of the part is approximated. Based on this, the hemming parameters such as flange length, roll-in, wrinkling and plastic strains are calculated for each of the geometric basic shapes by performing a meta-model-based segmental product validation. The metamodel is based on an element similar formulation that includes a reference dataset of various geometric basic shapes. A random automotive outer panel can now be analysed and optimized based on the hemming-specific database. By implementing this approach into a planning system, an efficient optimization of designing hemming processes will be enabled. Furthermore, valuable time and cost benefits can be realized in a vehicle’s development process.

Early-onset, slow progression of cone photoreceptor dysfunction and degeneration in CNG channel subunit CNGB3 deficiency.

PubMed

Xu, Jianhua; Morris, Lynsie; Fliesler, Steven J; Sherry, David M; Ding, Xi-Qin

2011-06-01

To investigate the progression of cone dysfunction and degeneration in CNG channel subunit CNGB3 deficiency. Retinal structure and function in CNGB3(-/-) and wild-type (WT) mice were evaluated by electroretinography (ERG), lectin cytochemistry, and correlative Western blot analysis of cone-specific proteins. Cone and rod terminal integrity was assessed by electron microscopy and synaptic protein immunohistochemical distribution. Cone ERG amplitudes (photopic b-wave) in CNGB3(-/-) mice were reduced to approximately 50% of WT levels by postnatal day 15, decreasing further to approximately 30% of WT levels by 1 month and to approximately 20% by 12 months of age. Rod ERG responses (scotopic a-wave) were not affected in CNGB3(-/-) mice. Average CNGB3(-/-) cone densities were approximately 80% of WT levels at 1 month and declined slowly thereafter to only approximately 50% of WT levels by 12 months. Expression levels of M-opsin, cone transducin α-subunit, and cone arrestin in CNGB3(-/-) mice were reduced by 50% to 60% by 1 month and declined to 35% to 45% of WT levels by 9 months. In addition, cone opsin mislocalized to the outer nuclear layer and the outer plexiform layer in the CNGB3(-/-) retina. Cone and rod synaptic marker expression and terminal ultrastructure were normal in the CNGB3(-/-) retina. These findings are consistent with an early-onset, slow progression of cone functional defects and cone loss in CNGB3(-/-) mice, with the cone signaling deficits arising from disrupted phototransduction and cone loss rather than from synaptic defects.

Advanced two-layer level set with a soft distance constraint for dual surfaces segmentation in medical images

NASA Astrophysics Data System (ADS)

Ji, Yuanbo; van der Geest, Rob J.; Nazarian, Saman; Lelieveldt, Boudewijn P. F.; Tao, Qian

2018-03-01

Anatomical objects in medical images very often have dual contours or surfaces that are highly correlated. Manually segmenting both of them by following local image details is tedious and subjective. In this study, we proposed a two-layer region-based level set method with a soft distance constraint, which not only regularizes the level set evolution at two levels, but also imposes prior information on wall thickness in an effective manner. By updating the level set function and distance constraint functions alternatingly, the method simultaneously optimizes both contours while regularizing their distance. The method was applied to segment the inner and outer wall of both left atrium (LA) and left ventricle (LV) from MR images, using a rough initialization from inside the blood pool. Compared to manual annotation from experience observers, the proposed method achieved an average perpendicular distance (APD) of less than 1mm for the LA segmentation, and less than 1.5mm for the LV segmentation, at both inner and outer contours. The method can be used as a practical tool for fast and accurate dual wall annotations given proper initialization.

Surface decarburization behavior and its adverse effects of air-cooled forging steel C70S6 for fracture splitting connecting rod

NASA Astrophysics Data System (ADS)

Zhang, Chao-lei; Xie, li-yao; Liu, Guang-lei; Chen, lie; Liu, Ya-zheng; Li, Jian

2016-09-01

Surface decarburization behavior and its adverse effects of air-cooled forging steel C70S6 for automobile engine fracture splitting connecting rod were investigated comprehensively by mechanical properties, microstructure and fracture morphology analysis. The results show that the surface decarburization in the outer surface of the fracture splitting at the big end bore and the micro-cracks in the decarburized layer are result in the uneven and spalling fracture surfaces of the waster connecting rod product. Besides, partial decarburization is produced between 900 °C and 1250 °C for heating 2 h, and decarburization sensitivity reach maximum at 1150 °C, but no complete decarburization forms for heating 2 h at 650-1250 °C. The decarburized depth follows a parabolic law with the increase of the heating time from 0.5 h to 12 h, and the decarburization sensitivity coefficient is 2.05×10-5 m·s-1/2 at 1200 °C. For the connecting rod manufacturing, surface decarburization must be under effective control during the hot forging process but not the control cooling process.

Translocation of "rod-coil" polymers: probing the structure of single molecules within nanopores.

PubMed

de Haan, Hendrick W; Slater, Gary W

2013-01-25

Using simulation and analytical techniques, we demonstrate that it is possible to extract structural information about biological molecules by monitoring the dynamics as they translocate through nanopores. From Langevin dynamics simulations of polymers exhibiting discrete changes in flexibility (rod-coil polymers), distinct plateaus are observed in the progression towards complete translocation. Characterizing these dynamics via an incremental mean first passage approach, the large steps are shown to correspond to local barriers preventing the passage of the coils while the rods translocate relatively easily. Analytical replication of the results provides insight into the corrugated nature of the free energy landscape as well as the dependence of the effective barrier heights on the length of the coil sections. Narrowing the width of the pore or decreasing the charge on either the rod or the coil segments are both shown to enhance the resolution of structural details. The special case of a single rod confined within a nanopore is also studied. Here, sufficiently long flexible sections attached to either end are demonstrated to act as entropic anchors which can effectively trap the rod within the pore for an extended period of time. Both sets of results suggest new experimental approaches for the control and study of biological molecules within nanopores.

Three-axis asymmetric radiation detector system

DOEpatents

Martini, Mario Pierangelo; Gedcke, Dale A.; Raudorf, Thomas W.; Sangsingkeow, Pat

2000-01-01

A three-axis radiation detection system whose inner and outer electrodes are shaped and positioned so that the shortest path between any point on the inner electrode and the outer electrode is a different length whereby the rise time of a pulse derived from a detected radiation event can uniquely define the azimuthal and radial position of that event, and the outer electrode is divided into a plurality of segments in the longitudinal axial direction for locating the axial location of a radiation detection event occurring in the diode.

Spine segmentation from C-arm CT data sets: application to region-of-interest volumes for spinal interventions

NASA Astrophysics Data System (ADS)

Buerger, C.; Lorenz, C.; Babic, D.; Hoppenbrouwers, J.; Homan, R.; Nachabe, R.; Racadio, J. M.; Grass, M.

2017-03-01

Spinal fusion is a common procedure to stabilize the spinal column by fixating parts of the spine. In such procedures, metal screws are inserted through the patients back into a vertebra, and the screws of adjacent vertebrae are connected by metal rods to generate a fixed bridge. In these procedures, 3D image guidance for intervention planning and outcome control is required. Here, for anatomical guidance, an automated approach for vertebra segmentation from C-arm CT images of the spine is introduced and evaluated. As a prerequisite, 3D C-arm CT images are acquired covering the vertebrae of interest. An automatic model-based segmentation approach is applied to delineate the outline of the vertebrae of interest. The segmentation approach is based on 24 partial models of the cervical, thoracic and lumbar vertebrae which aggregate information about (i) the basic shape itself, (ii) trained features for image based adaptation, and (iii) potential shape variations. Since the volume data sets generated by the C-arm system are limited to a certain region of the spine the target vertebra and hence initial model position is assigned interactively. The approach was trained and tested on 21 human cadaver scans. A 3-fold cross validation to ground truth annotations yields overall mean segmentation errors of 0.5 mm for T1 to 1.1 mm for C6. The results are promising and show potential to support the clinician in pedicle screw path and rod planning to allow accurate and reproducible insertions.

Diagnostic resonant cavity for a charged particle accelerator

DOEpatents

Barov, Nikolai

2007-10-02

Disclosed is a diagnostic resonant cavity for determining characteristics of a charged particle beam, such as an electron beam, produced in a charged particle accelerator. The cavity is based on resonant quadrupole-mode and higher order cavities. Enhanced shunt impedance in such cavities is obtained by the incorporation of a set of four or more electrically conductive rods extending inwardly from either one or both of the end walls of the cavity, so as to form capacitive gaps near the outer radius of the beam tube. For typical diagnostic cavity applications, a five-fold increase in shunt impedance can be obtained. In alternative embodiments the cavity may include either four or more opposing pairs of rods which extend coaxially toward one another from the opposite end walls of the cavity and are spaced from one another to form capacitative gaps; or the cavity may include a single set of individual rods that extend from one end wall to a point adjacent the opposing end wall.

Dynamic fatigue behaviour of Ag-doped Bi-2212 textured thin rods

NASA Astrophysics Data System (ADS)

Madre, M. A.; Rasekh, Sh; Diez, J. C.; Sotelo, A.

2009-03-01

The flexural strength of 1 wt.% Ag-doped Bi2Sr2CaCu2O8+δ thin rods textured by a laser heated floating zone was measured as a function of the environmental conditions (air versus water) at room temperature. Loading rates spanning three orders of magnitude (1, 10 and 100 μm/min) were used to explore their susceptibility to the environmental conditions. These mechanical tests were completed with electrical characterization (critical current at 77K and resistivity from 77 to 300 K) of samples submerged in distilled water for different time lengths (0, 12 and 120h). While Bi2Sr2CaCu2O8+δ has been shown, in previous works, to be unstable during contact with water molecules, the Ag-doped Bi-2212 textured rods tested in this work are very inert to the water environment, with respect to their mechanical and electrical properties, due to the presence of a narrow (approx150 μm) low textured outer ring formed in the growth process.

ACUTE ZONAL OCCULT OUTER RETINOPATHY: Structural and Functional Analysis Across the Transition Zone Between Healthy and Diseased Retina.

PubMed

Duncker, Tobias; Lee, Winston; Jiang, Fan; Ramachandran, Rithambara; Hood, Donald C; Tsang, Stephen H; Sparrow, Janet R; Greenstein, Vivienne C

2018-01-01

To assess structure and function across the transition zone (TZ) between relatively healthy and diseased retina in acute zonal occult outer retinopathy. Six patients (6 eyes; age 22-71 years) with acute zonal occult outer retinopathy were studied. Spectral-domain optical coherence tomography, fundus autofluorescence, near-infrared reflectance, color fundus photography, and fundus perimetry were performed and images were registered to each other. The retinal layers of the spectral-domain optical coherence tomography scans were segmented and the thicknesses of two outer retinal layers, that is, the total receptor and outer segment plus layers, and the retinal nerve fiber layer were measured. All eyes showed a TZ on multimodal imaging. On spectral-domain optical coherence tomography, the TZ was in the nasal retina at varying distances from the fovea. For all eyes, it was associated with loss of the ellipsoid zone band, significant thinning of the two outer retinal layers, and in three eyes with thickening of the retinal nerve fiber layer. On fundus autofluorescence, all eyes had a clearly demarcated peripapillary area of abnormal fundus autofluorescence delimited by a border of high autofluorescence; the latter was associated with loss of the ellipsoid zone band and with a change from relatively normal to markedly decreased or nonrecordable visual sensitivity on fundus perimetry. The results of multimodal imaging clarified the TZ in acute zonal occult outer retinopathy. The TZ was outlined by a distinct high autofluorescence border that correlated with loss of the ellipsoid zone band on spectral-domain optical coherence tomography. However, in fundus areas that seemed healthy on fundus autofluorescence, thinning of the outer retinal layers and thickening of the retinal nerve fiber layer were observed near the TZ. The TZ was also characterized by a decrease in visual sensitivity.

Taylor bubbles in liquid filled annuli: Some new observations

NASA Astrophysics Data System (ADS)

Agarwal, V.; Jana, A. K.; Das, G.; Das, P. K.

2007-10-01

Taylor bubbles rising through a vertical concentric annulus do not wrap around the inner tube completely. The two edges of the bubble are separated by a liquid bridge which increases with an increase of the inner radius. However, the change in the shape of the Taylor bubbles in annuli with extremely small inner diameter has not yet been reported. In the present investigation, several experiments have been performed in circular and noncircular annuli to understand the influence of the inner and outer wall on the bubble shape. The bubble has been observed to assume a completely different shape in both circular and square annuli with a very thin inner rod. Nevertheless, the rise velocity for such situations agree with the prediction of the model proposed by Das et al. [Chem. Eng. Sci. 53, 977 (1998)] when the outer pipe is circular but fails for a square outer pipe.

Increasing the feasibility of minimally invasive procedures in type A aortic dissections: a framework for segmentation and quantification.

PubMed

Morariu, Cosmin Adrian; Terheiden, Tobias; Dohle, Daniel Sebastian; Tsagakis, Konstantinos; Pauli, Josef

2016-02-01

Our goal is to provide precise measurements of the aortic dimensions in case of dissection pathologies. Quantification of surface lengths and aortic radii/diameters together with the visualization of the dissection membrane represents crucial prerequisites for enabling minimally invasive treatment of type A dissections, which always also imply the ascending aorta. We seek a measure invariant to luminance and contrast for aortic outer wall segmentation. Therefore, we propose a 2D graph-based approach using phase congruency combined with additional features. Phase congruency is extended to 3D by designing a novel conic directional filter and adding a lowpass component to the 3D Log-Gabor filterbank for extracting the fine dissection membrane, which separates the true lumen from the false one within the aorta. The result of the outer wall segmentation is compared with manually annotated axial slices belonging to 11 CTA datasets. Quantitative assessment of our novel 2D/3D membrane extraction algorithms has been obtained for 10 datasets and reveals subvoxel accuracy in all cases. Aortic inner and outer surface lengths, determined within 2 cadaveric CT datasets, are validated against manual measurements performed by a vascular surgeon on excised aortas of the body donors. This contribution proposes a complete pipeline for segmentation and quantification of aortic dissections. Validation against ground truth of the 3D contour lengths quantification represents a significant step toward custom-designed stent-grafts.

Biomechanical Evaluation of a Growth-Friendly Rod Construct

PubMed Central

Galvis, Sarah; Arnold, Josh; Mannen, Erin; Wong, Benjamin; Sis, Hadley; Cadel, Eileen; Anderson, John; Anderson, Dennis; Arnold, Paul; Friis, Elizabeth

2017-01-01

Background Distraction type rods mechanically stabilize the thorax and improve lung growth and function by applying distraction forces at the rib, spine, pelvis, or a combination of locations. However, the amount of stability the rods provide and the amount the thorax needs is unknown. Methods Five freshly frozen and thawed cadaveric thoracic spine specimens were tested lateral bending, flexion/extension, and axial rotation in displacement control (1°/sec) to a load limit of ± 5 Nm for five cycles after which a growth-friendly unilateral rod was placed in a simulated rib-to-lumbar attachment along the right side. The specimens were tested again the same modes of bending. From the seven Optotrak Orthopedic Research Pin markers (Northern Digital Inc., Waterloo, ON, Canada) inserted into the top potting to denote T1, and the right pedicles at T2, T4, T5, T8, T9, and T11 and the Standard Needle Tip Pressure Transducers (Gaeltech, Isle of Skye, Scotland) inserted into the T4/T5 and T8/T9 discs, motion, stiffness, and pressure data were calculated. Parameters from the third cycle of the intact case and the construct case were compared using two-tailed paired t-tests with 0.05 as the level of significance. Results With the construct attached, the T1–T4 segment showed a 30% increase in NZS during extension (p = 0.001); the T8–T12 segment experienced a 63% reduction in the in-plane ROM during flexion (p = 0.04); and the T8/T9 spinal motion unit had a significant decrease of 24% in EZS during left axial rotation (p = 0.04). Conclusions It’s clear the device as tested here does not produce large biomechanical changes, but the balance between providing desired changes while preventing complications remains difficult. Clinical Relevance Investigating the biomechanical effect growth-friendly rods have on the thoracic spine could lead to better understanding of treatment outcomes, both positive and negative. PMID:28038688

Evolution of Magnetic Rayleigh–Taylor Instability into the Outer Solar Corona and Low Interplanetary Space

NASA Astrophysics Data System (ADS)

Mishra, Sudheer K.; Singh, Talwinder; Kayshap, P.; Srivastava, A. K.

2018-03-01

We analyze the observations from Solar TErrestrial RElations Observatory (STEREO)-A and B/COR-1 of an eruptive prominence in the intermediate corona on 2011 June 7 at 08:45 UT, which consists of magnetic Rayleigh–Taylor (MRT) unstable plasma segments. Its upper-northward segment shows spatio-temporal evolution of MRT instability in form of finger structures up to the outer corona and low interplanetary space. Using the method of Dolei et al., It is estimated that the density in each bright finger is greater than the corresponding dark region lying below it in the surrounding intermediate corona. The instability is evolved due to wave perturbations that are parallel to the magnetic field at the density interface. We conjecture that the prominence plasma is supported by tension component of the magnetic field against gravity. Through the use of linear stability theory, the magnetic field is estimated as 21–40 mG to suppress growth of MRT instability in the observed finger structures. In the southward plasma segment, a horn-like structure is observed at 11:55 UT in the intermediate corona that also indicates MRT instability. Falling blobs are also observed in both of the plasma segments. In the outer corona, up to 6–13 solar radii, the mushroom-like plasma structures have been identified in the upper-northward MRT unstable plasma segment using STEREO-A/COR-2. These structures most likely grew due to the breaking and twisting of fingers at large spatial scales in weaker magnetic fields. In the lower interplanetary space up to 20 solar radii, these structures are fragmented into various small-scale localized plasma spikes, most likely due to turbulent mixing.

Development of a composite geodetic structure for space construction, phase 2

NASA Technical Reports Server (NTRS)

1981-01-01

Primary physical and mechanical properties were defined for pultruded hybrid HMS/E-glass P1700 rod material used for the fabrication of geodetic beams. Key properties established were used in the analysis, design, fabrication, instrumentation, and testing of a geodetic parameter cylinder and a lattice cone closeout joined to a short cylindrical geodetic beam segment. Requirements of structural techniques were accomplished. Analytical procedures were refined and extended to include the effect of rod dimensions for the helical and longitudinal members on local buckling, and the effect of different flexural and extensional moduli on general instability buckling.

METHOD AND APPARATUS FOR FABRICATING TUBULAR UNITS

DOEpatents

Haldeman, G.W.

1959-02-24

A method and apparatus are described for fabricating tubular assemblies such as clad fuel elements for nuclear reactors. According to this method, a plurality of relatively short cylindrical slug-shaped members are inserted in an outer protective tubular jacket, and the assembly is passed through a reducing die to draw the outer tubular member into tight contact with the slug members, the slugs being automatically spaced with respect to each other and helium being inserted during the drawing operation to fill the spaces. The apparatus includes a pusher rod which functions to space the slugelements equidistantly by pushing on them in the direction of drawing but traveling at a slower rate than that of the tubular member.

Dielectric supported radio-frequency cavities

DOEpatents

Yu, David U. L.; Lee, Terry G.

2000-01-01

A device which improves the electrical and thermomechanical performance of an RF cavity, for example, in a disk-loaded accelerating structure. A washer made of polycrystalline diamond is brazed in the middle to a copper disk washer and at the outer edge to the plane wave transformer tank wall, thus dissipating heat from the copper disk to the outer tank wall while at the same time providing strong mechanical support to the metal disk. The washer structure eliminates the longitudinal connecting rods and cooling channels used in the currently available cavities, and as a result minimizes problems such as shunt impedance degradation and field distortion in the plane wave transformer, and mechanical deflection and uneven cooling of the disk assembly.

Trabecular Bone Strength Predictions of HR-pQCT and Individual Trabeculae Segmentation (ITS)-Based Plate and Rod Finite Element Model Discriminate Postmenopausal Vertebral Fractures

PubMed Central

Liu, X. Sherry; Wang, Ji; Zhou, Bin; Stein, Emily; Shi, Xiutao; Adams, Mark; Shane, Elizabeth; Guo, X. Edward

2013-01-01

While high-resolution peripheral quantitative computed tomography (HR-pQCT) has advanced clinical assessment of trabecular bone microstructure, nonlinear microstructural finite element (μFE) prediction of yield strength by HR-pQCT voxel model is impractical for clinical use due to its prohibitively high computational costs. The goal of this study was to develop an efficient HR-pQCT-based plate and rod (PR) modeling technique to fill the unmet clinical need for fast bone strength estimation. By using individual trabecula segmentation (ITS) technique to segment the trabecular structure into individual plates and rods, a patient-specific PR model was implemented by modeling each trabecular plate with multiple shell elements and each rod with a beam element. To validate this modeling technique, predictions by HR-pQCT PR model were compared with those of the registered high resolution μCT voxel model of 19 trabecular sub-volumes from human cadaveric tibiae samples. Both Young’s modulus and yield strength of HR-pQCT PR models strongly correlated with those of μCT voxel models (r2=0.91 and 0.86). Notably, the HR-pQCT PR models achieved major reductions in element number (>40-fold) and CPU time (>1,200-fold). Then, we applied PR model μFE analysis to HR-pQCT images of 60 postmenopausal women with (n=30) and without (n=30) a history of vertebral fracture. HR-pQCT PR model revealed significantly lower Young’s modulus and yield strength at the radius and tibia in fracture subjects compared to controls. Moreover, these mechanical measurements remained significantly lower in fracture subjects at both sites after adjustment for aBMD T-score at the ultradistal radius or total hip. In conclusion, we validated a novel HR-pQCT PR model of human trabecular bone against μCT voxel models and demonstrated its ability to discriminate vertebral fracture status in postmenopausal women. This accurate nonlinear μFE prediction of HR-pQCT PR model, which requires only seconds of desktop computer time, has tremendous promise for clinical assessment of bone strength. PMID:23456922

49 CFR 236.710 - Block, latch.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 49 Transportation 4 2010-10-01 2010-10-01 false Block, latch. 236.710 Section 236.710 Transportation Other Regulations Relating to Transportation (Continued) FEDERAL RAILROAD ADMINISTRATION... Block, latch. The lower extremity of a latch rod which engages with a square shoulder of the segment or...

Live-Cell Imaging of Phagosome Motility in Primary Mouse RPE Cells.

PubMed

Hazim, Roni; Jiang, Mei; Esteve-Rudd, Julian; Diemer, Tanja; Lopes, Vanda S; Williams, David S

2016-01-01

The retinal pigment epithelium (RPE) is a post-mitotic epithelial monolayer situated between the light-sensitive photoreceptors and the choriocapillaris. Given its vital functions for healthy vision, the RPE is a primary target for insults that result in blinding diseases, including age-related macular degeneration (AMD). One such function is the phagocytosis and digestion of shed photoreceptor outer segments. In the present study, we examined the process of trafficking of outer segment disk membranes in live cultures of primary mouse RPE, using high speed spinning disk confocal microscopy. This approach has enabled us to track phagosomes, and determine parameters of their motility, which are important for their efficient degradation.

Foveal cone spacing and cone photopigment density difference: objective measurements in the same subjects.

PubMed

Marcos, S; Tornow, R P; Elsner, A E; Navarro, R

1997-07-01

Foveal cone spacing was measured in vivo using an objective technique: ocular speckle interferometry. Cone packing density was computed from cone spacing data. Foveal cone photopigment density difference was measured in the same subjects using retinal densitometry with a scanning laser ophthalmoscope. Both the cone packing density and cone photopigment density difference decreased sharply with increasing retinal eccentricity. From the comparison of both sets of measurements, the computed amounts of photopigment per cone increased slightly with increasing retinal eccentricity. Consistent with previous results, decreases in cone outer segment length are over-compensated by an increase in the outer segment area, at least in retinal eccentricities up to 1 deg.

Shoreline configuration and shoreline dynamics: A mesoscale analysis. [Assateague Island and Outer Banks of North Carolina

NASA Technical Reports Server (NTRS)

Dolan, R. (Principal Investigator); Hayden, B. P.; Heywood, J. E.

1975-01-01

The author has identified the following significant results. Atlantic coast barrier island shorelines are seldom straight, but rather sinuous. These shoreline curvatures range in size from cusps to capes. Significant relationships exist between the orientation of shoreline segments within the larger of these sinuous features and shoreline dynamics, with coefficients ranging up to .9. Orientation of the shoreline segments of Assateague Island (60 km) and the Outer Banks of North Carolina (130 km) was measured from LANDSAT 2 imagery (1:80,000) and high altitude aerial photography (1:120,000). Long term trends in shoreline dynamics were established by mapping shoreline and storm-surge penetration changes.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ketusky, E.

The U.S. Department of Energy’s (DOE’s) Used Fuel Disposition Campaign (UFDC) Program has transported high-burnup nuclear sister fuel rods from a commercial nuclear power plant for purposes of evaluation and testing. The evaluation and testing of high-burnup used nuclear fuel is integral to DOE initiatives to collect information useful in determining the integrity of fuel cladding for future safe transportation of the fuel, and for determining the effects of aging, on the integrity of UNF subjected to extended storage and subsequent transportation. The UFDC Program, in collaboration with the U.S. Nuclear Regulatory Commission and the commercial nuclear industry, has obtainedmore » individual used nuclear fuel rods for testing. The rods have been received at Oak Ridge National Laboratory (ORNL) for both separate effects testing (SET) and small-scale testing (SST). To meet the research objectives, testing on multiple 6 inch fuel rod pins cut from the rods at ORNL will be performed at Pacific Northwest National Laboratory (PNNL). Up to 10 rod equivalents will be shipped. Options were evaluated for multiple shipments using the 10-160B (based on 4.5 rod equivalents) and a single shipment using the NAC-LWT. Based on the original INL/Virginia Power transfer agreement, the rods are assumed to 152 inches in length with a 0.374-inch diameter. This report provides a preliminary content evaluation for use of the 10-160B and NAC-LWT for transporting those fuel rod pins from ORNL to PNNL. This report documents the acceptability of using these packagings to transport the fuel segments from ORNL to PNNL based on the following evaluations: enrichment, A2 evaluation, Pu-239 FGE evaluation, heat load, shielding (both gamma and neutron), and content weight/structural evaluation.« less

Late Complication of Surgically Treated Atlantoaxial Instability: Occipital Bone Erosion Induced by Protruded Fixed Titanium Rod: A Case Report

PubMed Central

Nakao, Yaoki; Shimokawa, Nobuyuki; Morisako, Hiroki; Tsukazaki, Yuji; Terada, Aiko; Nakajo, Kosuke; Fu, Yoshihiko

2014-01-01

Objective Polyaxial screw-rod fixation of C1-C2 is a relatively new technique to treat atlantoaxial instability, and there have been few reports in the literature outlining all possible complications. The purpose of this case report is to present the occurrence and management of occipital bone erosion induced by the protruded rostral part of a posterior atlantoaxial screw-rod construct causing headache. Clinical Features A 70-year-old Asian man with rheumatoid arthritis initially presented to our institution with atlantoaxial instability causing progressive quadraparesis and neck pain. Intervention and Outcome Posterior atlantoaxial instrumented fixation using C1 lateral mass screws in conjunction with C2 pedicle screws was performed to stabilize these segments. Postoperatively, the patient regained the ability to independently walk and had no radiographic evidence of instrumentation hardware failure and excellent sagittal alignment. However, despite a well-stabilized fusion, the patient began to complain of headache during neck extension. Follow-up imaging studies revealed left occipital bone erosion induced by a protruded titanium rod fixed with setscrews. During revision surgery, the rod protrusion was modified and the headaches diminished. Conclusion This case demonstrates that occipital bone erosion after posterior atlantoaxial fixation causing headache may occur. The principal cause of bone erosion in this case was rod protrusion. Although posterior atlantoaxial fixation using the screw-rod system was selected to manage atlantoaxial instability because it has less complications than other procedures, surgeons should pay attention that the length of the rod protrusion should not exceed 2 mm. PMID:25435842

A novel technique to study pore-forming peptides in a natural membrane.

PubMed

Vedovato, Natascia; Rispoli, Giorgio

2007-09-01

The biophysical characteristics and the pore formation dynamics of synthetic or naturally occurring peptides forming membrane-spanning channels were investigated by using isolated photoreceptor rod outer segments (OS) recorded in whole-cell configuration. Once blocking the two OS endogenous conductances (the cGMP channels by light and the Na(+):Ca(2+),K(+) exchanger by removing one of the transported ion species from both sides of the membrane, i.e. K(+), Na(+) or Ca(2+)), the OS membrane resistance (R ( m )) was typically larger than 1 GOmega in the presence of 1 mM external Ca(2+). Therefore, any exogenous current could be studied down to the single channel level. The peptides were applied to (and removed from) the extracellular OS side in approximately 50 ms with a computer-controlled microperfusion system, in which every perfusion parameter, as the rate of solution flow, the temporal sequence of solution changes or the number of automatic, self-washing cycles were controlled by a user-friendly interface. This technique was then used to determine the biophysical properties and the pore formation dynamics of antibiotic peptaibols, as the native alamethicin mixture, the synthesized major component of the neutral fraction (F50/5) of alamethicin, and the synthetic trichogin GA IV.

Effect of surfactants and natural detergents on phosphatidylcholine synthesis in photoreceptor membranes.

PubMed

Roque, M E; Castagnet, P I; Giusto, N M

2001-07-01

The synthesis of phosphatidylcholine (PC) in rod outer segments (ROS) catalysed by lysophosphatidylcholine acyltransferase and phosphatidylethanolamine N-methyltransferase (PE N-MTase) was studied and the effects of natural (FA and lysophospholipids) and synthetic (Triton X-100, deoxycholate and CHAPS) surfactants was evaluated. In all experimental conditions used, incorporation of labelled oleate into lysophosphatidylcholine (lysoPC) was at least 40 times greater than oleate incorporation into any other lysophospholipid. Acylation of lysoPC was slightly affected by Triton X-100 and was totally inhibited in the presence of 10 mM sodium deoxycholate (NaDOC) or CHAPS. Below their critical micelle concentration (cmc) Triton X-100 and NaDOC stimulated acylation of all ROS lysophospholipids analysed. The activity of PE N-MTase was stimulated at detergent concentrations below the cmc and inhibited at concentrations above the cmc for all three detergents tested. The effect of FA with differing degree of unsaturation on PC synthesis was evaluated. Oleic acid (10 microM) inhibited methyl group incorporation into total PC, whereas from 100 microM onward, the methylating activity increased with preferential synthesis of PC. Docosahexaenoic acid, in turn, inhibited PE N-MTase activity at every concentration tested. These results suggest that PC synthesis in ROS membranes is modified by bioregulators and surfactants altering the physico-chemical state of the membrane.

pH-dependent interaction of rhodopsin with cyanidin-3-glucoside. 2. Functional aspects.

PubMed

Tirupula, Kalyan C; Balem, Fernanda; Yanamala, Naveena; Klein-Seetharaman, Judith

2009-01-01

Anthocyanins are a class of phytochemicals that confer color to flowers, fruits, vegetables and leaves. They are part of our regular diet and serve as dietary supplements because of numerous health benefits, including improved vision. Recent studies have shown that the anthocyanin cyanidin-3-O-glucoside (C3G) increased regeneration of the dim-light photoreceptor rhodopsin (Matsumoto et al. [2003] J. Agric. Food Chem., 51, 3560-3563). In an accompanying study (Yanamala et al. [2009] Photochem. Photobiol.), we show that C3G directly binds to rhodopsin in a pH-dependent manner. In this study, we investigated the functional consequences of C3G binding to rhodopsin. As observed previously in rod outer segments, regeneration of purified rhodopsin in detergent micelles is also accelerated in the presence of C3G. Thermal denaturation and stability studies using circular dichroism, fluorescence and UV/visible absorbance spectroscopy show that C3G exerts a destabilizing effect on rhodopsin structure while it only modestly alters G-protein activation and the rates at which the light-activated Metarhodopsin II state decays to opsin and free retinal. These results indicate that the mechanism of C3G-enhanced regeneration may be based on changes in opsin structure promoting access to the retinal binding pocket.

Histochemical and ultrastructural studies on the calcareous corpuscles and eggs of Taenia taeniaeformis and Dipylidium caninum.

PubMed

Khalifa, Refaat M A; Mazen, Nawal A M; Marawan, Aziza M A; Thabit, Hasnaa T M

2011-08-01

Calcareous corpuscles were noticed by several previous workers to be present in larval and adult cestodes without knowing their function. However, nothing was mentioned in the available literature about distribution of these corpuscles and their density, structure and composition in different parts of the body of different cestodes. Hence, in the present work, a comparative study of their distribution, density, histochemical and ultrastructural characters in different parts of the body was performed in Taenia taeniaeformis and Dipylidium caninum. Due to the presence of the eggs in their gravid segments, their histochemical and ultrastructural characteristics were also studied. It was found that the size, location and density of the calcareous bodies were different in different body parts of the same and the other cestode. Histochemically, the main component of these corpuscles was calcium; while other constituents as polysaccharides, lipids, protrins and mucopolysaccharides were found in their outer rim. Ultrastructurally, they were quite similar in the two studied cestodes and different stages of their development were exhibited. Histochemically, the eggs of both cestodes were similar in their contents. However, some ultrastructural differences have been demonstrated particularly in relation to the size and shape of the rods in the embryophore and the structures in between the embryophore and onchosphere.

Oxidation mimicking substitution of conservative cysteine in recoverin suppresses its membrane association.

PubMed

Permyakov, Sergei E; Zernii, Evgeni Yu; Knyazeva, Ekaterina L; Denesyuk, Alexander I; Nazipova, Aliya A; Kolpakova, Tatiana V; Zinchenko, Dmitry V; Philippov, Pavel P; Permyakov, Eugene A; Senin, Ivan I

2012-04-01

Recoverin belongs to the family of intracellular Ca(2+)-binding proteins containing EF-hand domains, neuronal calcium sensors (NCS). In photoreceptor outer segments, recoverin is involved into the recovery of visual cycle via Ca(2+)-dependent interaction with disk membranes and inhibition of rhodopsin kinase. The function of a conservative within NCS family Cys residue in the inactive EF-loop 1 remains unclear, but previous study has shown its vulnerability to oxidation under mild oxidizing conditions. To elucidate the influence of oxidation of the conservative Cys39 in recoverin the properties of its C39D mutant, mimicking oxidative conversion of Cys39 into sulfenic, sulfinic or sulfonic acids have been studied using intrinsic fluorescence, circular dichroism, and equilibrium centrifugation methods. The C39D substitution results in essential changes in structural, physico-chemical and physiological properties of the protein: it reduces α-helical content, decreases thermal stability and suppresses protein affinity for photoreceptor membranes. The latter effect precludes proper functioning of the Ca(2+)-myristoyl switch in recoverin. The revealed significance of oxidation state of Cys39 for maintaining the protein functional status shows that it may serve as redox sensor in vision and suggests an explanation of the available data on localization and light-dependent translocation of recoverin in rod photoreceptors.

Structural Basis for Interactions Between Contactin Family Members and Protein-tyrosine Phosphatase Receptor Type G in Neural Tissues.

PubMed

Nikolaienko, Roman M; Hammel, Michal; Dubreuil, Véronique; Zalmai, Rana; Hall, David R; Mehzabeen, Nurjahan; Karuppan, Sebastian J; Harroch, Sheila; Stella, Salvatore L; Bouyain, Samuel

2016-10-07

Protein-tyrosine phosphatase receptor type G (RPTPγ/PTPRG) interacts in vitro with contactin-3-6 (CNTN3-6), a group of glycophosphatidylinositol-anchored cell adhesion molecules involved in the wiring of the nervous system. In addition to PTPRG, CNTNs associate with multiple transmembrane proteins and signal inside the cell via cis-binding partners to alleviate the absence of an intracellular region. Here, we use comprehensive biochemical and structural analyses to demonstrate that PTPRG·CNTN3-6 complexes share similar binding affinities and a conserved arrangement. Furthermore, as a first step to identifying PTPRG·CNTN complexes in vivo, we found that PTPRG and CNTN3 associate in the outer segments of mouse rod photoreceptor cells. In particular, PTPRG and CNTN3 form cis-complexes at the surface of photoreceptors yet interact in trans when expressed on the surfaces of apposing cells. Further structural analyses suggest that all CNTN ectodomains adopt a bent conformation and might lie parallel to the cell surface to accommodate these cis and trans binding modes. Taken together, these studies identify a PTPRG·CNTN complex in vivo and provide novel insights into PTPRG- and CNTN-mediated signaling. © 2016 by The American Society for Biochemistry and Molecular Biology, Inc.

Recirculating electric air filter

DOEpatents

Bergman, Werner

1986-01-01

An electric air filter cartridge has a cylindrical inner high voltage eleode, a layer of filter material, and an outer ground electrode formed of a plurality of segments moveably connected together. The outer electrode can be easily opened to remove or insert filter material. Air flows through the two electrodes and the filter material and is exhausted from the center of the inner electrode.

Recirculating electric air filter

DOEpatents

Bergman, W.

1985-01-09

An electric air filter cartridge has a cylindrical inner high voltage electrode, a layer of filter material, and an outer ground electrode formed of a plurality of segments moveably connected together. The outer electrode can be easily opened to remove or insert filter material. Air flows through the two electrodes and the filter material and is exhausted from the center of the inner electrode.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Jy-An John; Wang, Hong; Jiang, Hao

The objective of this project is to perform a systematic study of SNF/UNF (spent nuclear fuel/or used nuclear fuel) integrity under simulated transportation environments by using hot cell testing technology developed recently at Oak Ridge National Laboratory (ORNL), CIRFT (Cyclic Integrated Reversible-Bending Fatigue Tester). Under Nuclear Regulatory Commission (NRC) sponsorship, ORNL completed four benchmarking tests, four static tests, and twelve dynamic or cycle tests on H. B. Robinson (HBR) high burn-up (HBU) fuel. With support from the US Department of Energy and the NRC, CIRFT testing has been continued. The CIRFT testing was conducted on three HBR rods (R3, R4,more » and R5), with two specimens failed and one specimen un-failed. The total number of cycles in the test of un-failed specimens went over 2.23 107; the test was stopped as because the specimen did not show any sign of failure. The data analysis on all the HBR SNF rods demonstrated that it is necessary to characterize the fatigue life of used fuel rods in terms of both the curvature amplitude and the maximum of absolute of curvature extremes. The latter is significant because the maxima of extremes signify the maximum of tensile stress of the outer fiber of the bending rod. So far, a large variety of hydrogen contents has been covered in the CIRFT testing on HBR rods. It has been shown that the load amplitude is the dominant factor that controls the lifetime of bending rods, but the hydrogen content also has an important effect on the lifetime attained, according to the load range tested.« less

Method for preparing spherical thermoplastic particles of uniform size

DOEpatents

Day, J.R.

1975-11-17

Spherical particles of thermoplastic material of virtually uniform roundness and diameter are prepared by cutting monofilaments of a selected diameter into rod-like segments of a selected uniform length which are then heated in a viscous liquid to effect the formation of the spherical particles.

Design and Operation of a Calorimeter for Advanced Multilayer Insulation Testing

NASA Technical Reports Server (NTRS)

Chato, David J.; Johnson, Wesley L.; Van Dresar, Neil

2016-01-01

A calorimeter has been constructed to accurately measure insulation performance with a nominal 90K outer boundary and a 20K inner boundary. Unique features of this design include use of mechanical cryocoolers instead of cryogens and measurement of the heat load with a calibrated heat conduction rod. The calorimeter is operational and has completed its first test series. The initial test series was designed to look for differences in performance between a single layer of aluminum foil and a sheet of double aluminized Mylar (DAM). Although it has been speculated that the aluminum foil would perform better, since the aluminum coating on the Mylar might not be thick enough to stop the transmission of long wave length infrared radiation, our testing showed a higher heat load for the aluminum foil than the DAM. The aluminum foil showed a heat load of 132 mW at an 87 K outer temperature and 152 mW at a 107K outer temperature, whereas the DAM showed a heat load of 66 mW at an 88 K outer temperature and 81 mW at 108 K.

Design and Operation of a Calorimeter for Advanced Multilayer Insulation Testing

NASA Technical Reports Server (NTRS)

Chato, David; Johnson, Wesley; Dresar, Neil Van

2016-01-01

A calorimeter has been constructed to accurately measure insulation performance with a nominal 90K cold outer boundary and a 20K inner boundary. Unique features of this design include use of mechanical cryocoolers instead cryogens and measurement of the heat load with a calibrated rod to serve as a conduction path. The calorimeter is operational and has completed its first test series. The initial test series was designed to look for differences in performance between a single layer of aluminum foil and a sheet of double aluminized mylar (DAM). Although it has been speculated that the aluminum foil would perform better, since the mylar coating might not thick enough to stop the transmission of long wave length infrared radiation, our testing showed a higher heat load for the aluminum foil than the DAM. The aluminum foil showed a heat load of 132 mW at an 87 K outer temperature and 152 mW at a 107K outer temperature. Whereas the DAM showed a heat load of 66 mW at an 88 K outer temperature and 81 mW at 108 K.

The Cellular Origins of the Outer Retinal Bands in Optical Coherence Tomography Images

PubMed Central

Jonnal, Ravi S.; Kocaoglu, Omer P.; Zawadzki, Robert J.; Lee, Sang-Hyuck; Werner, John S.; Miller, Donald T.

2014-01-01

Purpose. To test the recently proposed hypothesis that the second outer retinal band, observed in clinical OCT images, originates from the inner segment ellipsoid, by measuring: (1) the thickness of this band within single cone photoreceptors, and (2) its respective distance from the putative external limiting membrane (band 1) and cone outer segment tips (band 3). Methods. Adaptive optics-optical coherence tomography images were acquired from four subjects without known retinal disease. Images were obtained at foveal (2°) and perifoveal (5°) locations. Cone photoreceptors (n = 9593) were identified and segmented in three dimensions using custom software. Features corresponding to bands 1, 2, and 3 were automatically identified. The thickness of band 2 was assessed in each cell by fitting the longitudinal reflectance profile of the band with a Gaussian function. Distances between bands 1 and 2, and between 2 and 3, respectively, were also measured in each cell. Two independent calibration techniques were employed to determine the depth scale (physical length per pixel) of the imaging system. Results. When resolved within single cells, the thickness of band 2 is a factor of three to four times narrower than in corresponding clinical OCT images. The distribution of band 2 thickness across subjects and eccentricities had a modal value of 4.7 μm, with 48% of the cones falling between 4.1 and 5.2 μm. No significant differences were found between cells in the fovea and perifovea. The distance separating bands 1 and 2 was found to be larger than the distance between bands 2 and 3, across subjects and eccentricities, with a significantly larger difference at 5° than 2°. Conclusions. On the basis of these findings, we suggest that ascription of the outer retinal band 2 to the inner segment ellipsoid is unjustified, because the ellipsoid is both too thick and proximally located to produce the band. PMID:25324288

Temporary Segmental Distraction in a Dog with Degenerative Lumbosacral Stenosis.

PubMed

Willems, Nicole; Kersten, Roel F M R; van Gaalen, Steven M; Öner, F Cumhur; Strijkers, Gustav J; Veraa, Stefanie; Beukers, Martijn; Tryfonidou, Marianna A; Meij, Björn P

2018-06-02

 Degenerative lumbosacral stenosis (DLSS) is characterized by intervertebral disc degeneration and causes lower back pain in dogs. Temporary distraction in rabbit models with induced intervertebral disc degeneration showed signs of intervertebral disc repair. In the present study, we assessed safety and efficacy of temporary segmental distraction in a dog with clinical signs of DLSS.  Distraction of the lumbosacral junction by pedicle screw-rod fixation was applied in a 5-year-old Greyhound with DLSS and evaluated by radiography, magnetic resonance imaging, and force plate analysis before and after distraction.  Safe distraction of the lumbosacral junction was demonstrated, with improvement of clinical signs after removal of the distraction device. Signal intensity of the intervertebral disc showed no changes over time. T2 value was highest directly after removal of the distraction device but decreased by 10% of the preoperative value at 9 months of follow-up. Disc height decreased (8%) immediately after removal of the distraction device, but recovered to the initial value. A decrease in the pelvic/thoracic propulsive force during pedicle screw-rod fixation and distraction was demonstrated, which slowly increased by 4% compared with the initial value.  Temporary pedicle screw-rod fixation in combination with distraction in a dog with DLSS was safe, improved clinical signs and retained disc height at 9 months of follow-up. Schattauer GmbH Stuttgart.

Automated segmentation of mouse OCT volumes (ASiMOV): Validation & clinical study of a light damage model.

PubMed

Antony, Bhavna Josephine; Kim, Byung-Jin; Lang, Andrew; Carass, Aaron; Prince, Jerry L; Zack, Donald J

2017-01-01

The use of spectral-domain optical coherence tomography (SD-OCT) is becoming commonplace for the in vivo longitudinal study of murine models of ophthalmic disease. Longitudinal studies, however, generate large quantities of data, the manual analysis of which is very challenging due to the time-consuming nature of generating delineations. Thus, it is of importance that automated algorithms be developed to facilitate accurate and timely analysis of these large datasets. Furthermore, as the models target a variety of diseases, the associated structural changes can also be extremely disparate. For instance, in the light damage (LD) model, which is frequently used to study photoreceptor degeneration, the outer retina appears dramatically different from the normal retina. To address these concerns, we have developed a flexible graph-based algorithm for the automated segmentation of mouse OCT volumes (ASiMOV). This approach incorporates a machine-learning component that can be easily trained for different disease models. To validate ASiMOV, the automated results were compared to manual delineations obtained from three raters on healthy and BALB/cJ mice post LD. It was also used to study a longitudinal LD model, where five control and five LD mice were imaged at four timepoints post LD. The total retinal thickness and the outer retina (comprising the outer nuclear layer, and inner and outer segments of the photoreceptors) were unchanged the day after the LD, but subsequently thinned significantly (p < 0.01). The retinal nerve fiber-ganglion cell complex and the inner plexiform layers, however, remained unchanged for the duration of the study.

Automated segmentation of mouse OCT volumes (ASiMOV): Validation & clinical study of a light damage model

PubMed Central

Lang, Andrew; Carass, Aaron; Prince, Jerry L.; Zack, Donald J.

2017-01-01

The use of spectral-domain optical coherence tomography (SD-OCT) is becoming commonplace for the in vivo longitudinal study of murine models of ophthalmic disease. Longitudinal studies, however, generate large quantities of data, the manual analysis of which is very challenging due to the time-consuming nature of generating delineations. Thus, it is of importance that automated algorithms be developed to facilitate accurate and timely analysis of these large datasets. Furthermore, as the models target a variety of diseases, the associated structural changes can also be extremely disparate. For instance, in the light damage (LD) model, which is frequently used to study photoreceptor degeneration, the outer retina appears dramatically different from the normal retina. To address these concerns, we have developed a flexible graph-based algorithm for the automated segmentation of mouse OCT volumes (ASiMOV). This approach incorporates a machine-learning component that can be easily trained for different disease models. To validate ASiMOV, the automated results were compared to manual delineations obtained from three raters on healthy and BALB/cJ mice post LD. It was also used to study a longitudinal LD model, where five control and five LD mice were imaged at four timepoints post LD. The total retinal thickness and the outer retina (comprising the outer nuclear layer, and inner and outer segments of the photoreceptors) were unchanged the day after the LD, but subsequently thinned significantly (p < 0.01). The retinal nerve fiber-ganglion cell complex and the inner plexiform layers, however, remained unchanged for the duration of the study. PMID:28817571

Automatic plaque characterization and vessel wall segmentation in magnetic resonance images of atherosclerotic carotid arteries

NASA Astrophysics Data System (ADS)

Adame, Isabel M.; van der Geest, Rob J.; Wasserman, Bruce A.; Mohamed, Mona; Reiber, Johan H. C.; Lelieveldt, Boudewijn P. F.

2004-05-01

Composition and structure of atherosclerotic plaque is a primary focus of cardiovascular research. In vivo MRI provides a meanse to non-invasively image and assess the morphological features of athersclerotic and normal human carotid arteries. To quantitatively assess the vulnerability and the type of plaque, the contours of the lumen, outer boundary of the vessel wall and plaque components, need to be traced. To achieve this goal, we have developed an automated contou detection technique, which consists of three consecutive steps: firstly, the outer boundary of the vessel wall is detected by means of an ellipse-fitting procedure in order to obtain smoothed shapes; secondly, the lumen is segnented using fuzzy clustering. Thre region to be classified is that within the outer vessel wall boundary obtained from the previous step; finally, for plaque detection we follow the same approach as for lumen segmentation: fuzzy clustering. However, plaque is more difficult to segment, as the pixel gray value can differ considerably from one region to another, even when it corresponds to the same type of tissue. That makes further processing necessary. All these three steps might be carried out combining information from different sequences (PD-, T2-, T1-weighted images, pre- and post-contrast), to improve the contour detection. The algorithm has been validated in vivo on 58 high-resolution PD and T1 weighted MR images (19 patients). The results demonstrate excellent correspondence between automatic and manual area measurements: lumen (r=0.94), outer (r=0.92), and acceptable for fibrous cap thickness (r=0.76).

Hybrid circumferential fixation for degenerative lumbosacral spine disease: posterior lumbar interbody fusion plus universal clamp rod-band instrumentation: a novel technique for lumbosacral fixation.

PubMed

Tegos, Stergios; Charitidis, Charalampos; Korovessis, Panagiotis G

2014-04-01

Retrospective study on circumferential hybrid instrumentation with posterior lumbar interbody fusion (PLIF) and the novel posterior Universal Clamp (UC) instrumentation. This study evaluated the roentgenographic and clinical outcome after PLIF with PEEK cage augmented with UC posterior sublaminar fixation without posterior fusion. Although UC has been successfully used in scoliosis surgery, to our knowledge, this is the first report on its use in degenerative lumbosacral disease. Rigid pedicle screw lumbosacral fixation is associated with several intraoperative screw-related complications. The use of sublaminar bands and rods combined with PEEK PLIF should increase fusion rate and avoid screw-related complications. From a total of 295 consecutive patients who experienced degenerative lumbosacral disease and received posterior decompression, implantation of PLIF with PEEK cages and semirigid posterior fixation with sublaminar UC bands-rods without posterolateral fusion, 150 patients were eligible for this study with a follow-up of more than 2 years. Interbody fusion rate and global plus segmental sagittal spinal lordosis restoration were recorded pre- and postoperatively. Visual analogue scale and Oswestry Disability Index were used to assess functional outcome. Hybrid instrumentation expanded over 1 to 5 levels. Surgical time ranged from 45 to 225 minutes. Only 12.6% of the patients were transfused. There was no nerve root lesion or deep wound infection. Laminar fracture occurred intraoperatively in one case during band insertion. Interbody fusion was achieved in 94% of the operated segments. Lumbar lordosis improved from -36 ± 9° preoperatively to -53 ± 6° postoperatively. Segmental lordosis improved in L4-L5 segment from -5 ± 3° preoperatively to -12 ± 2° postoperatively and in L5-S1 from -9 ± 4° to -14 ± 2° postoperation. Oswestry Disability Index score improved from 44.9 preoperatively to 2.2 postoperatively (P < 0.001). No patient required further spinal surgery until the final evaluation. UC, a novel semirigid sublaminar posterior instrumentation, combined with wedge-shaped PEEK PLIF corrected both global and segmental sagittal lumbar alignment and achieved fusion rate similar to that historically reported with pedicle screw-PLIF techniques, however, avoiding intraoperative complications associated with the use of pedicle screws.

Store-operated channels regulate intracellular calcium in mammalian rods

PubMed Central

Molnar, Tünde; Barabas, Peter; Birnbaumer, Lutz; Punzo, Claudio; Kefalov, Vladimir; Križaj, David

2012-01-01

Exposure to daylight closes cyclic nucleotide-gated (CNG) and voltage-operated Ca2+-permeable channels in mammalian rods. The consequent lowering of the cytosolic calcium concentration ([Ca2+]i), if protracted, can contribute to light-induced damage and apoptosis in these cells. We here report that mouse rods are protected against prolonged lowering of [Ca2+]i by store-operated Ca2+ entry (SOCE). Ca2+ stores were depleted in Ca2+-free saline supplemented with the endoplasmic reticulum (ER) sequestration blocker cyclopiazonic acid. Store depletion elicited [Ca2+]i signals that exceeded baseline [Ca2+]i by 5.9 ± 0.7-fold and were antagonized by an inhibitory cocktail containing 2-APB, SKF 96365 and Gd3+. Cation influx through SOCE channels was sufficient to elicit a secondary activation of L-type voltage-operated Ca2+ entry. We also found that TRPC1, the type 1 canonical mammalian homologue of the Drosophila photoreceptor TRP channel, is predominantly expressed within the outer nuclear layer of the retina. Rod loss in Pde6brd1 (rd1), Chx10/Kip1−/−rd1 and Elovl4TG2 dystrophic models was associated with ∼70% reduction in Trpc1 mRNA content whereas Trpc1 mRNA levels in rodless cone-full Nrl−/− retinas were decreased by ∼50%. Genetic ablation of TRPC1 channels, however, had no effect on SOCE, the sensitivity of the rod phototransduction cascade or synaptic transmission at rod and cone synapses. Thus, we localized two new mechanisms, SOCE and TRPC1, to mammalian rods and characterized the contribution of SOCE to Ca2+ homeostasis. By preventing the cytosolic [Ca2+]i from dropping too low under sustained saturating light conditions, these signalling pathways may protect Ca2+-dependent mechanisms within the ER and the cytosol without affecting normal rod function. PMID:22674725

Pyrometer mount for a closed-circuit thermal medium cooled gas turbine

DOEpatents

Jones, Raymond Joseph; Kirkpatrick, Francis Lawrence; Burns, James Lee; Fulton, John Robert

2002-01-01

A steam-cooled second-stage nozzle segment has an outer band and an outer cover defining a plenum therebetween for receiving cooling steam for flow through the nozzles to the inner band and cover therefor and return flow through the nozzles. To measure the temperature of the buckets of the stage forwardly of the nozzle stage, a pyrometer boss is electron beam-welded in an opening through the outer band and TIG-welded to the outer cover plate. By machining a hole through the boss and seating a linearly extending tube in the boss, a line of sight between a pyrometer mounted on the turbine frame and the buckets is provided whereby the temperature of the buckets can be ascertained. The welding of the boss to the outer band and outer cover enables steam flow through the plenum without leakage, while providing a line of sight through the outer cover and outer band to measure bucket temperature.

Inner and outer coronary vessel wall segmentation from CCTA using an active contour model with machine learning-based 3D voxel context-aware image force

NASA Astrophysics Data System (ADS)

Sivalingam, Udhayaraj; Wels, Michael; Rempfler, Markus; Grosskopf, Stefan; Suehling, Michael; Menze, Bjoern H.

2016-03-01

In this paper, we present a fully automated approach to coronary vessel segmentation, which involves calcification or soft plaque delineation in addition to accurate lumen delineation, from 3D Cardiac Computed Tomography Angiography data. Adequately virtualizing the coronary lumen plays a crucial role for simulating blood ow by means of fluid dynamics while additionally identifying the outer vessel wall in the case of arteriosclerosis is a prerequisite for further plaque compartment analysis. Our method is a hybrid approach complementing Active Contour Model-based segmentation with an external image force that relies on a Random Forest Regression model generated off-line. The regression model provides a strong estimate of the distance to the true vessel surface for every surface candidate point taking into account 3D wavelet-encoded contextual image features, which are aligned with the current surface hypothesis. The associated external image force is integrated in the objective function of the active contour model, such that the overall segmentation approach benefits from the advantages associated with snakes and from the ones associated with machine learning-based regression alike. This yields an integrated approach achieving competitive results on a publicly available benchmark data collection (Rotterdam segmentation challenge).

Disease expression in Usher syndrome caused by VLGR1 gene mutation (USH2C) and comparison with USH2A phenotype.

PubMed

Schwartz, Sharon B; Aleman, Tomas S; Cideciyan, Artur V; Windsor, Elizabeth A M; Sumaroka, Alexander; Roman, Alejandro J; Rane, Tej; Smilko, Elaine E; Bennett, Jean; Stone, Edwin M; Kimberling, William J; Liu, Xue-Zhong; Jacobson, Samuel G

2005-02-01

To investigate the retinal disease expression in USH2C, the subtype of Usher syndrome type 2 recently shown to be caused by mutation in the VLGR1 gene, and compare results with those from USH2A, a more common cause of Usher syndrome. Three siblings with USH2C and 14 patients with USH2A were studied. Visual function was measured by kinetic perimetry, static chromatic perimetry, and electroretinography (ERG). Central retinal microstructure was studied with optical coherence tomography (OCT). The siblings with VLGR1 mutation showed abnormal photoreceptor-mediated function in all retinal regions, and there was greater rod than cone dysfunction. USH2A had a wider spectrum of disease expression and included patients with normal function in some retinal regions. When abnormalities were detected, there was more rod than cone dysfunction. Retinal microstructure in both USH2C and USH2A shared the abnormality of loss of outer nuclear layer thickness. Central retinal structure in both genotypes was complicated by cystic macular lesions. A coincidental finding in an USH2C patient was that oral intake of antihistamines was associated with temporary resolution of the macular cystic change. USH2C and USH2A manifest photoreceptor disease with rod- and cone-mediated visual losses and thinning of the outer nuclear layer. An orderly progression through disease stages was estimated from cross-sectional and limited longitudinal data. Intrafamilial and interfamilial variation in retinal severity in USH2A, however, suggests that genetic or nongenetic modifiers may be involved in the disease expression.

Early-Onset, Slow Progression of Cone Photoreceptor Dysfunction and Degeneration in CNG Channel Subunit CNGB3 Deficiency

PubMed Central

Xu, Jianhua; Morris, Lynsie; Fliesler, Steven J.; Sherry, David M.

2011-01-01

Purpose. To investigate the progression of cone dysfunction and degeneration in CNG channel subunit CNGB3 deficiency. Methods. Retinal structure and function in CNGB3−/− and wild-type (WT) mice were evaluated by electroretinography (ERG), lectin cytochemistry, and correlative Western blot analysis of cone-specific proteins. Cone and rod terminal integrity was assessed by electron microscopy and synaptic protein immunohistochemical distribution. Results. Cone ERG amplitudes (photopic b-wave) in CNGB3−/− mice were reduced to approximately 50% of WT levels by postnatal day 15, decreasing further to approximately 30% of WT levels by 1 month and to approximately 20% by 12 months of age. Rod ERG responses (scotopic a-wave) were not affected in CNGB3−/− mice. Average CNGB3−/− cone densities were approximately 80% of WT levels at 1 month and declined slowly thereafter to only approximately 50% of WT levels by 12 months. Expression levels of M-opsin, cone transducin α-subunit, and cone arrestin in CNGB3−/− mice were reduced by 50% to 60% by 1 month and declined to 35% to 45% of WT levels by 9 months. In addition, cone opsin mislocalized to the outer nuclear layer and the outer plexiform layer in the CNGB3−/− retina. Cone and rod synaptic marker expression and terminal ultrastructure were normal in the CNGB3−/− retina. Conclusions. These findings are consistent with an early-onset, slow progression of cone functional defects and cone loss in CNGB3−/− mice, with the cone signaling deficits arising from disrupted phototransduction and cone loss rather than from synaptic defects. PMID:21273547

Progression of Pro23His Retinopathy in a Miniature Swine Model of Retinitis Pigmentosa

PubMed Central

Scott, Patrick A.; de Castro, Juan P. Fernandez; DeMarco, Paul J.; Ross, Jason W.; Njoka, Josephat; Walters, Eric; Prather, Randall S.; McCall, Maureen A.; Kaplan, Henry J.

2017-01-01

Purpose We characterize the progression of retinopathy in Filial 1 (F1) progeny of a transgenic (Tg) founder miniswine exhibiting severe Pro23His (P23H) retinopathy. Methods The F1 TgP23H miniswine progeny were created by crossing TgP23H founder miniswine 53-1 with wild type (WT) inbred miniature swine. Scotopic (rod-driven) and photopic (cone-driven) retinal functions were evaluated in F1 TgP23H and WT littermates using full field electroretinograms (ffERGs) at 1, 2, 3, 6, 9, 12, and 18 months of age, as well as the Tg founder miniswine at 6 years of age. Miniswine were euthanized and their retinas processed for morphologic evaluation at the light and electron microscopic level. Retinal morphology of a 36-month-old Tg miniswine also was examined. Results Wild type littermates reached mature scotopic and photopic retinal function by 3 months, while TgP23H miniswine showed abnormal scotopic ffERGs at the earliest time point, 1 month, and depressed photopic ffERGs after 2 months. Rod and cone photoreceptors (PR) exhibited morphologic abnormalities and dropout from the outer nuclear layer at 1 month, with only a monolayer of cone PR somata remaining after 2 months. The retinas showed progressive neural remodeling of the outer retina that included dendritic retraction of rod bipolar cells and glial seal formation by Müller cells. The TgP23H founder miniswine showed cone PR with relatively intact morphology exclusive to the area centralis. Conclusions The F1 Tg miniswine and the TgP23H founder miniswine exhibit similar retinopathy. Translational Relevance TgP23H miniswine are a useful large-eye model to study pathogenesis and preservation cone PRs in humans with retinitis pigmentosa. PMID:28316877

Serial imaging and structure-function correlates of high-density rings of fundus autofluorescence in retinitis pigmentosa.

PubMed

Robson, Anthony G; Tufail, Adnan; Fitzke, Fred; Bird, Alan C; Moore, Anthony T; Holder, Graham E; Webster, Andrew R

2011-09-01

To document the evolution and functional and structural significance of parafoveal rings of high-density fundus autofluorescence (AF) in patients with retinitis pigmentosa and preserved visual acuity. Fifty-two patients with nonsyndromic retinitis pigmentosa or Usher syndrome, who had a parafoveal ring of high-density AF and a visual acuity of 20/30 or better, were ascertained. All had international standard full-field electroretinography and pattern electroretinography. Autofluorescence imaging was repeated in 30 patients after periods of up to 9.3 years. Of the 52 patients, 35 underwent optical coherence tomography. Progressive constriction of the ring was detected in 17 patients. Ring radius reduced by up to 40% at a mean rate of between 0.8% and 15.8% per year. In 1 patient, a small ring was replaced by irregular AF; visual acuity deteriorated over the same period. There was a high correspondence between the lateral extent of the preserved optical coherence tomography inner segment/outer segment band and the diameter of the ring along the same optical coherence tomographic scan plane (slope, 0.9; r = 0.97; P < 0.005; n = 35) and between preserved inner segment/outer segment lamina and the pattern electroretinography P50 measure of macular function (R = 0.72; P < 0.005; n = 34). Rings of increased AF surround areas of preserved outer retina and preserved photopic function. Serial fundus AF may provide prognostic indicators for preservation of central acuity and potentially assist in the identification and evaluation of patients suitable for treatment aimed at preservation of remaining function.

Improving image segmentation performance and quantitative analysis via a computer-aided grading methodology for optical coherence tomography retinal image analysis.

PubMed

Debuc, Delia Cabrera; Salinas, Harry M; Ranganathan, Sudarshan; Tátrai, Erika; Gao, Wei; Shen, Meixiao; Wang, Jianhua; Somfai, Gábor M; Puliafito, Carmen A

2010-01-01

We demonstrate quantitative analysis and error correction of optical coherence tomography (OCT) retinal images by using a custom-built, computer-aided grading methodology. A total of 60 Stratus OCT (Carl Zeiss Meditec, Dublin, California) B-scans collected from ten normal healthy eyes are analyzed by two independent graders. The average retinal thickness per macular region is compared with the automated Stratus OCT results. Intergrader and intragrader reproducibility is calculated by Bland-Altman plots of the mean difference between both gradings and by Pearson correlation coefficients. In addition, the correlation between Stratus OCT and our methodology-derived thickness is also presented. The mean thickness difference between Stratus OCT and our methodology is 6.53 microm and 26.71 microm when using the inner segment/outer segment (IS/OS) junction and outer segment/retinal pigment epithelium (OS/RPE) junction as the outer retinal border, respectively. Overall, the median of the thickness differences as a percentage of the mean thickness is less than 1% and 2% for the intragrader and intergrader reproducibility test, respectively. The measurement accuracy range of the OCT retinal image analysis (OCTRIMA) algorithm is between 0.27 and 1.47 microm and 0.6 and 1.76 microm for the intragrader and intergrader reproducibility tests, respectively. Pearson correlation coefficients demonstrate R(2)>0.98 for all Early Treatment Diabetic Retinopathy Study (ETDRS) regions. Our methodology facilitates a more robust and localized quantification of the retinal structure in normal healthy controls and patients with clinically significant intraretinal features.

Improving image segmentation performance and quantitative analysis via a computer-aided grading methodology for optical coherence tomography retinal image analysis

NASA Astrophysics Data System (ADS)

Cabrera Debuc, Delia; Salinas, Harry M.; Ranganathan, Sudarshan; Tátrai, Erika; Gao, Wei; Shen, Meixiao; Wang, Jianhua; Somfai, Gábor M.; Puliafito, Carmen A.

2010-07-01

We demonstrate quantitative analysis and error correction of optical coherence tomography (OCT) retinal images by using a custom-built, computer-aided grading methodology. A total of 60 Stratus OCT (Carl Zeiss Meditec, Dublin, California) B-scans collected from ten normal healthy eyes are analyzed by two independent graders. The average retinal thickness per macular region is compared with the automated Stratus OCT results. Intergrader and intragrader reproducibility is calculated by Bland-Altman plots of the mean difference between both gradings and by Pearson correlation coefficients. In addition, the correlation between Stratus OCT and our methodology-derived thickness is also presented. The mean thickness difference between Stratus OCT and our methodology is 6.53 μm and 26.71 μm when using the inner segment/outer segment (IS/OS) junction and outer segment/retinal pigment epithelium (OS/RPE) junction as the outer retinal border, respectively. Overall, the median of the thickness differences as a percentage of the mean thickness is less than 1% and 2% for the intragrader and intergrader reproducibility test, respectively. The measurement accuracy range of the OCT retinal image analysis (OCTRIMA) algorithm is between 0.27 and 1.47 μm and 0.6 and 1.76 μm for the intragrader and intergrader reproducibility tests, respectively. Pearson correlation coefficients demonstrate R2>0.98 for all Early Treatment Diabetic Retinopathy Study (ETDRS) regions. Our methodology facilitates a more robust and localized quantification of the retinal structure in normal healthy controls and patients with clinically significant intraretinal features.

Fully automated calculation of cardiothoracic ratio in digital chest radiographs

NASA Astrophysics Data System (ADS)

Cong, Lin; Jiang, Luan; Chen, Gang; Li, Qiang

2017-03-01

The calculation of Cardiothoracic Ratio (CTR) in digital chest radiographs would be useful for cardiac anomaly assessment and heart enlargement related disease indication. The purpose of this study was to develop and evaluate a fully automated scheme for calculation of CTR in digital chest radiographs. Our automated method consisted of three steps, i.e., lung region localization, lung segmentation, and CTR calculation. We manually annotated the lung boundary with 84 points in 100 digital chest radiographs, and calculated an average lung model for the subsequent work. Firstly, in order to localize the lung region, generalized Hough transform was employed to identify the upper, lower, and outer boundaries of lung by use of Sobel gradient information. The average lung model was aligned to the localized lung region to obtain the initial lung outline. Secondly, we separately applied dynamic programming method to detect the upper, lower, outer and inner boundaries of lungs, and then linked the four boundaries to segment the lungs. Based on the identified outer boundaries of left lung and right lung, we corrected the center and the declination of the original radiography. Finally, CTR was calculated as a ratio of the transverse diameter of the heart to the internal diameter of the chest, based on the segmented lungs. The preliminary results on 106 digital chest radiographs showed that the proposed method could obtain accurate segmentation of lung based on subjective observation, and achieved sensitivity of 88.9% (40 of 45 abnormalities), and specificity of 100% (i.e. 61 of 61 normal) for the identification of heart enlargements.

Contrast visual acuity in patients with retinitis pigmentosa assessed by a contrast sensitivity tester.

PubMed

Oishi, Maho; Nakamura, Hajime; Hangai, Masanori; Oishi, Akio; Otani, Atsushi; Yoshimura, Nagahisa

2012-01-01

To assess contrast visual acuity (CVA) in patients with retinitis pigmentosa (RP) and compare the result with standard visual acuity (VA), retinal thickness, status of inner segment/outer segment junction, and central visual field. Thirty-nine eyes of 39 patients with RP and 39 eyes of 39 healthy individuals were studied. To see the difference in CVA between RP patients and normal controls, only subjects with standard VA of 1.0 (20/20) or better were included. This was a cross-sectional study. CVA in various light conditions was measured with CAT-2000 and was compared between patients and controls. CVA of patients was further analyzed for association with other parameters including foveal retinal thickness, outer nuclear layer thickness, the status of inner segment/outer segment junction measured with optical coherence tomography (OCT), and visual field mean deviation (MD) measured with Humphrey field analyzer 10-2 program. CVA impairment was evident in RP patients compared to controls (P < 0.01, in all measurement conditions). Multivariate analysis showed association of logarithm of the minimum angle of resolution (logMAR) with CVAs in several conditions. None of the OCT measurements was associated with CVA. When patients were divided into three groups based on MD, the most advanced group (MD worse than or equal to -20 dB) showed impairment of mesopic CVA (P < 0.05, under mesopic condition of 100% without glare, with glare, and 25% without glare). CVA impairment was confirmed in RP patients, especially in advanced cases. CVA measured with CAT-2000 may be a useful tool for assessing foveal function in RP patients.

Tether Deployer And Brake

NASA Technical Reports Server (NTRS)

Carroll, Joseph A.; Alexander, Charles M.

1993-01-01

Design concept promises speed, control, and reliability. Scheme for deploying tether provides for fast, free, and snagless payout and fast, dependable braking. Developed for small, expendable tethers in outer space, scheme also useful in laying transoceanic cables, deploying guidance wires to torpedoes and missiles, paying out rescue lines from ship to ship via rockets, deploying antenna wires, releasing communication and power cables to sonobuoys and expendable bathythermographs, and in reeling out lines from fishing rods.

A semi-automatic computer-aided method for surgical template design

NASA Astrophysics Data System (ADS)

Chen, Xiaojun; Xu, Lu; Yang, Yue; Egger, Jan

2016-02-01

This paper presents a generalized integrated framework of semi-automatic surgical template design. Several algorithms were implemented including the mesh segmentation, offset surface generation, collision detection, ruled surface generation, etc., and a special software named TemDesigner was developed. With a simple user interface, a customized template can be semi- automatically designed according to the preoperative plan. Firstly, mesh segmentation with signed scalar of vertex is utilized to partition the inner surface from the input surface mesh based on the indicated point loop. Then, the offset surface of the inner surface is obtained through contouring the distance field of the inner surface, and segmented to generate the outer surface. Ruled surface is employed to connect inner and outer surfaces. Finally, drilling tubes are generated according to the preoperative plan through collision detection and merging. It has been applied to the template design for various kinds of surgeries, including oral implantology, cervical pedicle screw insertion, iliosacral screw insertion and osteotomy, demonstrating the efficiency, functionality and generality of our method.

A semi-automatic computer-aided method for surgical template design

PubMed Central

Chen, Xiaojun; Xu, Lu; Yang, Yue; Egger, Jan

2016-01-01

This paper presents a generalized integrated framework of semi-automatic surgical template design. Several algorithms were implemented including the mesh segmentation, offset surface generation, collision detection, ruled surface generation, etc., and a special software named TemDesigner was developed. With a simple user interface, a customized template can be semi- automatically designed according to the preoperative plan. Firstly, mesh segmentation with signed scalar of vertex is utilized to partition the inner surface from the input surface mesh based on the indicated point loop. Then, the offset surface of the inner surface is obtained through contouring the distance field of the inner surface, and segmented to generate the outer surface. Ruled surface is employed to connect inner and outer surfaces. Finally, drilling tubes are generated according to the preoperative plan through collision detection and merging. It has been applied to the template design for various kinds of surgeries, including oral implantology, cervical pedicle screw insertion, iliosacral screw insertion and osteotomy, demonstrating the efficiency, functionality and generality of our method. PMID:26843434

A semi-automatic computer-aided method for surgical template design.

PubMed

Chen, Xiaojun; Xu, Lu; Yang, Yue; Egger, Jan

2016-02-04

This paper presents a generalized integrated framework of semi-automatic surgical template design. Several algorithms were implemented including the mesh segmentation, offset surface generation, collision detection, ruled surface generation, etc., and a special software named TemDesigner was developed. With a simple user interface, a customized template can be semi- automatically designed according to the preoperative plan. Firstly, mesh segmentation with signed scalar of vertex is utilized to partition the inner surface from the input surface mesh based on the indicated point loop. Then, the offset surface of the inner surface is obtained through contouring the distance field of the inner surface, and segmented to generate the outer surface. Ruled surface is employed to connect inner and outer surfaces. Finally, drilling tubes are generated according to the preoperative plan through collision detection and merging. It has been applied to the template design for various kinds of surgeries, including oral implantology, cervical pedicle screw insertion, iliosacral screw insertion and osteotomy, demonstrating the efficiency, functionality and generality of our method.

A New Species of Hyperbenthic Cyclopoid Copepod from Japan: First Record of the Genus Cyclopicina in the Indo-Pacific Region.

PubMed

Ohtsuka, Susumu; Tanaka, Hayato; Boxshall, Geoffrey A

2016-12-01

A new species of the cyclopinid genus Cyclopicina, C. toyoshioae sp. nov., was collected from the hyperbenthic layer off northern Kyushu Island, Japan; its description is based on two adult female specimens. This is the first record of the genus from the Indo-Pacific region. The new species can be distinguished from its two known congeners in: (1) the relatively short antennules which do not reach the posterior margin of the dorsal cephalothoracic shield; (2) the shape of seminal receptacles; (3) the segmentation and armature of the cephalothoracic appendages; (4) the shape of the basal protrusion between the rami of legs 1-4; (5) the presence of three outer spines on the third exopodal segment of leg 4; and (6) the presence or absence of outer setae on the free exopodal segment of leg 5. The genus Cyclopicina shows a wide but scattered distribution in hyperbenthic layers, from the continental shelves to deep-sea basins, in the northern hemisphere.

Structure and Composition of Isolated Core-Shell (In ,Ga )N /GaN Rods Based on Nanofocus X-Ray Diffraction and Scanning Transmission Electron Microscopy

NASA Astrophysics Data System (ADS)

Krause, Thilo; Hanke, Michael; Nicolai, Lars; Cheng, Zongzhe; Niehle, Michael; Trampert, Achim; Kahnt, Maik; Falkenberg, Gerald; Schroer, Christian G.; Hartmann, Jana; Zhou, Hao; Wehmann, Hergo-Heinrich; Waag, Andreas

2017-02-01

Nanofocus x-ray diffraction is used to investigate the structure and local strain field of an isolated (In ,Ga )N /GaN core-shell microrod. Because the high spatial resolution of the x-ray beam is only 80 ×90 nm2, we are able to investigate several distinct volumes on one individual side facet. Here, we find a drastic increase in thickness of the outer GaN shell along the rod height. Additionally, we performed high-angle annular dark-field scanning-transmission-electron-microscopy measurements on several rods from the same sample showing that (In,Ga)N double-quantum-well and GaN barrier thicknesses also increase strongly along the height. Moreover, plastic relaxation is observed in the top part of the rod. Based on the experimentally obtained structural parameters, we simulate the strain-induced deformation using the finite-element method, which serves as the input for subsequent kinematic scattering simulations. The simulations reveal a significant increase of elastic in-plane relaxation along the rod height. However, at a certain height, the occurrence of plastic relaxation yields a decrease of the elastic strain. Because of the experimentally obtained structural input for the finite-element simulations, we can exclude unknown structural influences on the strain distribution, and we are able to translate the elastic relaxation into an indium concentration which increases by a factor of 4 from the bottom to the height where plastic relaxation occurs.

Photoreceptor inner segment ellipsoid band integrity on spectral domain optical coherence tomography

PubMed Central

Saxena, Sandeep; Srivastav, Khushboo; Cheung, Chui M; Ng, Joanne YW; Lai, Timothy YY

2014-01-01

Spectral domain optical coherence tomography cross-sectional imaging of the macula has conventionally been resolved into four bands. However, some doubts were raised regarding authentication of the existence of these bands. Recently, a number of studies have suggested that the second band appeared to originate from the inner segment ellipsoids of the foveal cone photoreceptors, and therefore the previously called inner segment-outer segment junction is now referred to as inner segment ellipsoidband. Photoreceptor dysfunction may be a significant predictor of visual acuity in a spectrum of surgical and medical retinal diseases. This review aims to provide an overview and summarizes the role of the photoreceptor inner segment ellipsoid band in the management and prognostication of various vitreoretinal diseases. PMID:25525329

Neuroprotective effect of bilberry extract in a murine model of photo-stressed retina

PubMed Central

Osada, Hideto; Okamoto, Tomohiro; Kawashima, Hirohiko; Toda, Eriko; Miyake, Seiji; Nagai, Norihiro; Kobayashi, Saori; Tsubota, Kazuo; Ozawa, Yoko

2017-01-01

Excessive exposure to light promotes degenerative and blinding retinal diseases such as age-related macular degeneration and retinitis pigmentosa. However, the underlying mechanisms of photo-induced retinal degeneration are not fully understood, and a generalizable preventive intervention has not been proposed. Bilberry extract is an antioxidant-rich supplement that ameliorates ocular symptoms. However, its effects on photo-stressed retinas have not been clarified. In this study, we examined the neuroprotective effects of bilberry extract against photo-stress in murine retinas. Light-induced visual function impairment recorded by scotopic and phototopic electroretinograms showing respective rod and cone photoreceptor function was attenuated by oral administration of bilberry extract through a stomach tube in Balb/c mice (750 mg/kg body weight). Bilberry extract also suppressed photo-induced apoptosis in the photoreceptor cell layer and shortening of the outer segments of rod and cone photoreceptors. Levels of photo-induced reactive oxygen species (ROS), oxidative and endoplasmic reticulum (ER) stress markers, as measured by real-time reverse transcriptase polymerase chain reaction, were reduced by bilberry extract treatment. Reduction of ROS by N-acetyl-L-cysteine, a well-known antioxidant also suppressed ER stress. Immunohistochemical analysis of activating transcription factor 4 expression showed the presence of ER stress in the retina, and at least in part, in Müller glial cells. The photo-induced disruption of tight junctions in the retinal pigment epithelium was also attenuated by bilberry extract, repressing an oxidative stress marker, although ER stress markers were not repressed. Our results suggest that bilberry extract attenuates photo-induced apoptosis and visual dysfunction most likely, and at least in part, through ROS reduction, and subsequent ER stress attenuation in the retina. This study can help understand the mechanisms of photo-stress and contribute to developing a new, potentially useful therapeutic approach using bilberry extract for preventing retinal photo-damage. PMID:28570634

Neuroprotective effect of bilberry extract in a murine model of photo-stressed retina.

PubMed

Osada, Hideto; Okamoto, Tomohiro; Kawashima, Hirohiko; Toda, Eriko; Miyake, Seiji; Nagai, Norihiro; Kobayashi, Saori; Tsubota, Kazuo; Ozawa, Yoko

2017-01-01

Excessive exposure to light promotes degenerative and blinding retinal diseases such as age-related macular degeneration and retinitis pigmentosa. However, the underlying mechanisms of photo-induced retinal degeneration are not fully understood, and a generalizable preventive intervention has not been proposed. Bilberry extract is an antioxidant-rich supplement that ameliorates ocular symptoms. However, its effects on photo-stressed retinas have not been clarified. In this study, we examined the neuroprotective effects of bilberry extract against photo-stress in murine retinas. Light-induced visual function impairment recorded by scotopic and phototopic electroretinograms showing respective rod and cone photoreceptor function was attenuated by oral administration of bilberry extract through a stomach tube in Balb/c mice (750 mg/kg body weight). Bilberry extract also suppressed photo-induced apoptosis in the photoreceptor cell layer and shortening of the outer segments of rod and cone photoreceptors. Levels of photo-induced reactive oxygen species (ROS), oxidative and endoplasmic reticulum (ER) stress markers, as measured by real-time reverse transcriptase polymerase chain reaction, were reduced by bilberry extract treatment. Reduction of ROS by N-acetyl-L-cysteine, a well-known antioxidant also suppressed ER stress. Immunohistochemical analysis of activating transcription factor 4 expression showed the presence of ER stress in the retina, and at least in part, in Müller glial cells. The photo-induced disruption of tight junctions in the retinal pigment epithelium was also attenuated by bilberry extract, repressing an oxidative stress marker, although ER stress markers were not repressed. Our results suggest that bilberry extract attenuates photo-induced apoptosis and visual dysfunction most likely, and at least in part, through ROS reduction, and subsequent ER stress attenuation in the retina. This study can help understand the mechanisms of photo-stress and contribute to developing a new, potentially useful therapeutic approach using bilberry extract for preventing retinal photo-damage.

Vertebrate rod photoreceptors express both BK and IK calcium-activated potassium channels, but only BK channels are involved in receptor potential regulation.

PubMed

Pelucchi, Bruna; Grimaldi, Annalisa; Moriondo, Andrea

2008-01-01

In salamander rods, Ca(2+)-activated K(+) current (I(KCa)) provides an effective "clamp" of the dark membrane potential to its normal resting level. By a combination of electrophysiological, pharmacological, and immunohistochemical approaches, we show that salamander rods functionally express large-conductance Ca(2+)- and voltage-dependent potassium (BK) channel and intermediate-conductance Ca(2+)-dependent potassium (IK) channel, but not small-conductance Ca(2+)-dependent potassium channel (SK) subtypes. Application of 100 nM iberiotoxin and 100 nM clotrimazole reduced net I(KCa) to 36% and 63%, respectively, whereas the current was unaffected by application of 1 microM apamin. Consistently, anti- SK1, -SK2, and -SK3 antibodies were unable to stain rod photoreceptors, whereas both anti-BK and -SK4/ IK1 antibodies heavily stained the ellipsoid region of the inner segments of the rods. Moreover, by using current-clamp experiments, it was clearly seen that the strong clamping effect of the total I(KCa) was lost when IbTx, but not CLTZ, was applied to the bath. This behavior strongly suggests that of BK and IK channels, only the former are responsible for the clamping effect on the photoreceptor membrane potential.

Scoliosis corrective force estimation from the implanted rod deformation using 3D-FEM analysis.

PubMed

Abe, Yuichiro; Ito, Manabu; Abumi, Kuniyoshi; Sudo, Hideki; Salmingo, Remel; Tadano, Shigeru

2015-01-01

Improvement of material property in spinal instrumentation has brought better deformity correction in scoliosis surgery in recent years. The increase of mechanical strength in instruments directly means the increase of force, which acts on bone-implant interface during scoliosis surgery. However, the actual correction force during the correction maneuver and safety margin of pull out force on each screw were not well known. In the present study, estimated corrective forces and pull out forces were analyzed using a novel method based on Finite Element Analysis (FEA). Twenty adolescent idiopathic scoliosis patients (1 boy and 19 girls) who underwent reconstructive scoliosis surgery between June 2009 and Jun 2011 were included in this study. Scoliosis correction was performed with 6mm diameter titanium rod (Ti6Al7Nb) using the simultaneous double rod rotation technique (SDRRT) in all cases. The pre-maneuver and post-maneuver rod geometry was collected from intraoperative tracing and postoperative 3D-CT images, and 3D-FEA was performed with ANSYS. Cobb angle of major curve, correction rate and thoracic kyphosis were measured on X-ray images. Average age at surgery was 14.8, and average fusion length was 8.9 segments. Major curve was corrected from 63.1 to 18.1 degrees in average and correction rate was 71.4%. Rod geometry showed significant change on the concave side. Curvature of the rod on concave and convex sides decreased from 33.6 to 17.8 degrees, and from 25.9 to 23.8 degrees, respectively. Estimated pull out forces at apical vertebrae were 160.0N in the concave side screw and 35.6N in the convex side screw. Estimated push in force at LIV and UIV were 305.1N in the concave side screw and 86.4N in the convex side screw. Corrective force during scoliosis surgery was demonstrated to be about four times greater in the concave side than in convex side. Averaged pull out and push in force fell below previously reported safety margin. Therefore, the SDRRT maneuver was safe for correcting moderate magnitude curves. To prevent implant breakage or pedicle fracture during the maneuver in a severe curve correction, mobilization of spinal segment by releasing soft tissue or facet joint could be more important than using a stronger correction maneuver with a rigid implant.

Multicenter reliability of semiautomatic retinal layer segmentation using OCT

PubMed Central

Oberwahrenbrock, Timm; Traber, Ghislaine L.; Lukas, Sebastian; Gabilondo, Iñigo; Nolan, Rachel; Songster, Christopher; Balk, Lisanne; Petzold, Axel; Paul, Friedemann; Villoslada, Pablo; Brandt, Alexander U.; Green, Ari J.

2018-01-01

Objective To evaluate the inter-rater reliability of semiautomated segmentation of spectral domain optical coherence tomography (OCT) macular volume scans. Methods Macular OCT volume scans of left eyes from 17 subjects (8 patients with MS and 9 healthy controls) were automatically segmented by Heidelberg Eye Explorer (v1.9.3.0) beta-software (Spectralis Viewing Module v6.0.0.7), followed by manual correction by 5 experienced operators from 5 different academic centers. The mean thicknesses within a 6-mm area around the fovea were computed for the retinal nerve fiber layer, ganglion cell layer (GCL), inner plexiform layer (IPL), inner nuclear layer, outer plexiform layer (OPL), and outer nuclear layer (ONL). Intraclass correlation coefficients (ICCs) were calculated for mean layer thickness values. Spatial distribution of ICC values for the segmented volume scans was investigated using heat maps. Results Agreement between raters was good (ICC > 0.84) for all retinal layers, particularly inner retinal layers showed excellent agreement across raters (ICC > 0.96). Spatial distribution of ICC showed highest values in the perimacular area, whereas the ICCs were poorer for the foveola and the more peripheral macular area. The automated segmentation of the OPL and ONL required the most correction and showed the least agreement, whereas differences were less prominent for the remaining layers. Conclusions Automated segmentation with manual correction of macular OCT scans is highly reliable when performed by experienced raters and can thus be applied in multicenter settings. Reliability can be improved by restricting analysis to the perimacular area and compound segmentation of GCL and IPL. PMID:29552598

Reconstituted TOM core complex and Tim9/Tim10 complex of mitochondria are sufficient for translocation of the ADP/ATP carrier across membranes.

PubMed

Vasiljev, Andreja; Ahting, Uwe; Nargang, Frank E; Go, Nancy E; Habib, Shukry J; Kozany, Christian; Panneels, Valérie; Sinning, Irmgard; Prokisch, Holger; Neupert, Walter; Nussberger, Stephan; Rapaport, Doron

2004-03-01

Precursor proteins of the solute carrier family and of channel forming Tim components are imported into mitochondria in two main steps. First, they are translocated through the TOM complex in the outer membrane, a process assisted by the Tim9/Tim10 complex. They are passed on to the TIM22 complex, which facilitates their insertion into the inner membrane. In the present study, we have analyzed the function of the Tim9/Tim10 complex in the translocation of substrates across the outer membrane of mitochondria. The purified TOM core complex was reconstituted into lipid vesicles in which purified Tim9/Tim10 complex was entrapped. The precursor of the ADP/ATP carrier (AAC) was found to be translocated across the membrane of such lipid vesicles. Thus, these components are sufficient for translocation of AAC precursor across the outer membrane. Peptide libraries covering various substrate proteins were used to identify segments that are bound by Tim9/Tim10 complex upon translocation through the TOM complex. The patterns of binding sites on the substrate proteins suggest a mechanism by which portions of membrane-spanning segments together with flanking hydrophilic segments are recognized and bound by the Tim9/Tim10 complex as they emerge from the TOM complex into the intermembrane space.

Turbine nozzle stage having thermocouple guide tube

DOEpatents

Schotsch, Margaret Jones; Kirkpatrick, Francis Lawrence; Lapine, Eric Michael

2002-01-01

A guide tube is fixed adjacent opposite ends in outer and inner covers of a nozzle stage segment. The guide tube is serpentine in shape between the outer and inner covers and extends through a nozzle vane. An insert is disposed in the nozzle vane and has apertures to accommodate serpentine portions of the guide tube. Cooling steam is also supplied through chambers of the insert on opposite sides of a central insert chamber containing the guide tube. The opposite ends of the guide tube are fixed to sleeves, in turn fixed to the outer and inner covers.

Tank tread assemblies with track-linking mechanism

NASA Technical Reports Server (NTRS)

Collins, Earl R., Jr. (Inventor)

1986-01-01

The proposed tank tread assembly has adjacent tank tread segments joined by a link bearing tapered pins retained by clips inserted through the tread shells perpendicular to the axes of the pin. It also has highway pads attached by a release rod bearing tapered, grooved cams which interlockingly engage tabs inserted into the tread shells.

Flowing DPF Design for Propulsion Experiments

DTIC Science & Technology

1993-08-01

plasma acceleration but not a pinch i.e., added fusion energy , as envisioned in a DPF. The outer electrode at the UI DPF is constructed of 24 rods which...many respects to a coaxial plasma accelerator or a magnetic plasmoid accelerator, the added fusion energy supplied by the pinch step greatly enhances...modified DPF in space propulsion. Using a scaled-up model. From this model, the contribution of fusion energy to thrust and specific impulse is estimated

Architecture of kangaroo rat inner medulla: segmentation of descending thin limb of Henle's loop.

PubMed

Urity, Vinoo B; Issaian, Tadeh; Braun, Eldon J; Dantzler, William H; Pannabecker, Thomas L

2012-03-15

We hypothesize that the inner medulla of the kangaroo rat Dipodomys merriami, a desert rodent that concentrates its urine to more than 6,000 mosmol/kgH(2)O water, provides unique examples of architectural features necessary for production of highly concentrated urine. To investigate this architecture, inner medullary nephron segments in the initial 3,000 μm below the outer medulla were assessed with digital reconstructions from physical tissue sections. Descending thin limbs of Henle (DTLs), ascending thin limbs of Henle (ATLs), and collecting ducts (CDs) were identified by immunofluorescence using antibodies that label segment-specific proteins associated with transepithelial water flux (aquaporin 1 and 2, AQP1 and AQP2) and chloride flux (the chloride channel ClC-K1); all tubules and vessels were labeled with wheat germ agglutinin. In the outer 3,000 μm of the inner medulla, AQP1-positive DTLs lie at the periphery of groups of CDs. ATLs lie inside and outside the groups of CDs. Immunohistochemistry and reconstructions of loops that form their bends in the outer 3,000 μm of the inner medulla show that, relative to loop length, the AQP1-positive segment of the kangaroo rat is significantly longer than that of the Munich-Wistar rat. The length of ClC-K1 expression in the prebend region at the terminal end of the descending side of the loop in kangaroo rat is about 50% shorter than that of the Munich-Wistar rat. Tubular fluid of the kangaroo rat DTL may approach osmotic equilibrium with interstitial fluid by water reabsorption along a relatively longer tubule length, compared with Munich-Wistar rat. A relatively shorter-length prebend segment may promote a steeper reabsorptive driving force at the loop bend. These structural features predict functionality that is potentially significant in the production of a high urine osmolality in the kangaroo rat.

Macular telangiectasia type 2 (MacTel) in a 34-year-old patient.

PubMed

Nicolai, Heleen; Wirix, Mieke; Spielberg, Leigh; Leys, Anita

2014-09-23

We report macular telangiectasia type 2 (MacTel) in a 34-year-old man, the youngest patient so far published with MacTel type 2. The patient presented with metamorphopsia and impaired reading ability. Diagnosis was based on bilateral abnormal macular autofluorescence, perifoveal telangiectasia with fluorescein angiographic hyperfluorescence without cystoid oedema, a small foveal avascular zone, asymmetric configuration of the foveal pit, disruptions in the inner segment/outer segment layer and hyper-reflective haze and spots in the outer nuclear layer. Although MacTel usually manifests with a slowly progressive decrease in visual acuity in the fifth to seventh decades of life, younger patients may occasionally be diagnosed with the disease. Awareness of subtle signs of the condition is essential for early diagnosis. 2014 BMJ Publishing Group Ltd.

Macular telangiectasia type 2 (MacTel) in a 34-year-old patient

PubMed Central

Nicolai, Heleen; Wirix, Mieke; Spielberg, Leigh; Leys, Anita

2014-01-01

We report macular telangiectasia type 2 (MacTel) in a 34-year-old man, the youngest patient so far published with MacTel type 2. The patient presented with metamorphopsia and impaired reading ability. Diagnosis was based on bilateral abnormal macular autofluorescence, perifoveal telangiectasia with fluorescein angiographic hyperfluorescence without cystoid oedema, a small foveal avascular zone, asymmetric configuration of the foveal pit, disruptions in the inner segment/outer segment layer and hyper-reflective haze and spots in the outer nuclear layer. Although MacTel usually manifests with a slowly progressive decrease in visual acuity in the fifth to seventh decades of life, younger patients may occasionally be diagnosed with the disease. Awareness of subtle signs of the condition is essential for early diagnosis. PMID:25249218

A perspective of gene therapy in the glaucomas.

PubMed

Kaufman, P L; Jia, W W; Tan, J; Chen, Z; Gabelt, B T; Booth, V; Tufaro, F; Cynader, M

1999-06-01

Gene therapy in the anterior and posterior segment tissues may have the potential to favorably influence aqueous hydrodynamics and retinal ganglion cell biology, thereby preventing, delaying, or minimizing glaucomatous damage to the optic nerve. We demonstrated the feasibility of using a herpes viral vector (ribonucleotide reductase defective HSV-1, hrR3) to deliver the lacZ reporter gene to living cat and rat eyes. Cats received injections into the anterior chamber and rats into the vitreous cavity. In cats, lacZ expression was detectable at 1 to 2 days in the anterior outer portion of the ciliary muscle and the lining of the intertrabecular spaces of the corneoscleral and uveal meshwork. Rat eyes showed lacZ expression in the retinal pigment epithelium and photoreceptor outer segments 2 days after injection.

Autonomous motion of metallic microrods propelled by ultrasound.

PubMed

Wang, Wei; Castro, Luz Angelica; Hoyos, Mauricio; Mallouk, Thomas E

2012-07-24

Autonomously moving micro-objects, or micromotors, have attracted the attention of the scientific community over the past decade, but the incompatibility of phoretic motors with solutions of high ionic strength and the use of toxic fuels have limited their applications in biologically relevant media. In this letter we demonstrate that ultrasonic standing waves in the MHz frequency range can levitate, propel, rotate, align, and assemble metallic microrods (2 μm long and 330 nm diameter) in water as well as in solutions of high ionic strength. Metallic rods levitated to the midpoint plane of a cylindrical cell when the ultrasonic frequency was tuned to create a vertical standing wave. Fast axial motion of metallic microrods at ~200 μm/s was observed at the resonant frequency using continuous or pulsed ultrasound. Segmented metal rods (AuRu or AuPt) were propelled unidirectionally with one end (Ru or Pt, respectively) consistently forward. A self-acoustophoresis mechanism based on the shape asymmetry of the metallic rods is proposed to explain this axial propulsion. Metallic rods also aligned and self-assembled into long spinning chains, which in the case of bimetallic rods had a head-to-tail alternating structure. These chains formed ring or streak patterns in the levitation plane. The diameter or distance between streaks was roughly half the wavelength of the ultrasonic excitation. The ultrasonically driven movement of metallic rods was insensitive to the addition of salt to the solution, opening the possibility of driving and controlling metallic micromotors in biologically relevant media using ultrasound.

Fusionless instrumentation systems for congenital scoliosis: expandable spinal rods and vertical expandable prosthetic titanium rib in the management of congenital spine deformities in the growing child.

PubMed

Yazici, Muharrem; Emans, John

2009-08-01

Review of relevant literature including personal opinions. To review the current researches investigating the efficacy of growing rod and thoracic expansion techniques in the treatment of congenital spine deformity of young children, and to highlight the contrasting advantages and limitations in the fusionless treatment of progressive congenital scoliosis. Congenital scoliosis has the potential for severe spinal deformity and thoracic insufficiency syndrome (TIS). Conventional fusion treatments in children tend to shorten the spine further exacerbating trunk shortening and TIS. In the surgical treatment of congenital spinal deformities in young children, while reconstructing the spinal deformity, one should simultaneously pursue preserving the growth potential of the vertebrae, improving the volume, symmetry, and functions of the thorax, and protecting this improvement during the growth. Today, employed in the treatment of spinal deformities of young children, there are 2 deformity reconstruction methods serving these targets: Growing rod technique and vertical expandable prosthetic titanium rib (VEPTR) with or without expansion thoracostomy. Peer-reviewed research articles and major international meeting presentations were reviewed. Methods were compared in terms of advantages and limitations. The growing rod technique is a safe and reliable method in the treatment of congenital spine deformity of young children who present some flexibility in the anomalous segment, or when the congenital anomaly involves a vertebral segment too long for resection, or with compensating curve with structural pattern concomitant to the congenital deformity. Expansion thoracostomy and VEPTR are the appropriate choice for severe congenital spine deformity when a large amount of growth remains. Although ventilator dependence is significantly decreasing, thoracic volume and space available for the lung are increased after expansion thoracostomy and VEPTR. Growing rod technique should be used in patients where the primary problem is at the vertebral column. If the patient has rib fusions and/or TIS has developed, in other words, if the primary problem involves the thoracic cage, expansion thoracostomy and VEPTR should be an appropriate option.

Identification of the two rotavirus genes determining neutralization specificities

DOE Office of Scientific and Technical Information (OSTI.GOV)

Offit, P.A.; Blavat, G.

1986-01-01

Bovine rotavirus NCDV and simian rotavirus SA-11 represent two distinct rotavirus serotypes. A genetic approach was used to determine which viral gene segments segregated with serotype-specific viral neutralization. There were 16 reassortant rotarviruses derived by coinfection of MA-104 cells in vitro with the SA-11 and NCDV strains. The parental origin of reassortant rotavirus double-stranded RNA segments was determined by gene segment mobility in polyacrylamide gels and by hybridization with radioactively labeled parental viral transcripts. The authors found that two rotavirus gene segments found previously to code for outer capsid proteins vp3 and vp7 cosegreated with virus neutralization specificities.

Quartz ball valve

NASA Technical Reports Server (NTRS)

Goetz, C.; Ingle, W. M. (Inventor)

1980-01-01

A ball valve particularly suited for use in the handling of highly corrosive fluids is described. It is characterized by a valve housing formed of communicating segments of quartz tubing, a pair of communicating sockets disposed in coaxial alignment with selected segments of tubing for establishing a pair of inlet ports communicating with a common outlet port, a ball formed of quartz material supported for displacement between the sockets and configured to be received alternately thereby, and a valve actuator including a rod attached to the ball for selectively displacing the ball relative to each of the sockets for controlling fluid flow through the inlet ports.

Axially adjustable magnetic properties in arrays of multilayered Ni/Cu nanowires with variable segment sizes

NASA Astrophysics Data System (ADS)

Shirazi Tehrani, A.; Almasi Kashi, M.; Ramazani, A.; Montazer, A. H.

2016-07-01

Arrays of multilayered Ni/Cu nanowires (NWs) with variable segment sizes were fabricated into anodic aluminum oxide templates using a pulsed electrodeposition method in a single bath for designated potential pulse times. Increasing the pulse time between 0.125 and 2 s in the electrodeposition of Ni enabled the formation of segments with thicknesses ranging from 25 to 280 nm and 10-110 nm in 42 and 65 nm diameter NWs, respectively, leading to disk-shaped, rod-shaped and/or near wire-shaped geometries. Using hysteresis loop measurements at room temperature, the axial and perpendicular magnetic properties were investigated. Regardless of the segment geometry, the axial coercivity and squareness significantly increased with increasing Ni segment thickness, in agreement with a decrease in calculated demagnetizing factors along the NW length. On the contrary, the perpendicular magnetic properties were found to be independent of the pulse times, indicating a competition between the intrawire interactions and the shape demagnetizing field.

Relationship between photoreceptor outer segment length and visual acuity in diabetic macular edema.

PubMed

Forooghian, Farzin; Stetson, Paul F; Meyer, Scott A; Chew, Emily Y; Wong, Wai T; Cukras, Catherine; Meyerle, Catherine B; Ferris, Frederick L

2010-01-01

The purpose of this study was to quantify photoreceptor outer segment (PROS) length in 27 consecutive patients (30 eyes) with diabetic macular edema using spectral domain optical coherence tomography and to describe the correlation between PROS length and visual acuity. Three spectral domain-optical coherence tomography scans were performed on all eyes during each session using Cirrus HD-OCT. A prototype algorithm was developed for quantitative assessment of PROS length. Retinal thicknesses and PROS lengths were calculated for 3 parameters: macular grid (6 x 6 mm), central subfield (1 mm), and center foveal point (0.33 mm). Intrasession repeatability was assessed using coefficient of variation and intraclass correlation coefficient. The association between retinal thickness and PROS length with visual acuity was assessed using linear regression and Pearson correlation analyses. The main outcome measures include intrasession repeatability of macular parameters and correlation of these parameters with visual acuity. Mean retinal thickness and PROS length were 298 mum to 381 microm and 30 microm to 32 mum, respectively, for macular parameters assessed in this study. Coefficient of variation values were 0.75% to 4.13% for retinal thickness and 1.97% to 14.01% for PROS length. Intraclass correlation coefficient values were 0.96 to 0.99 and 0.73 to 0.98 for retinal thickness and PROS length, respectively. Slopes from linear regression analyses assessing the association of retinal thickness and visual acuity were not significantly different from 0 (P > 0.20), whereas the slopes of PROS length and visual acuity were significantly different from 0 (P < 0.0005). Correlation coefficients for macular thickness and visual acuity ranged from 0.13 to 0.22, whereas coefficients for PROS length and visual acuity ranged from -0.61 to -0.81. Photoreceptor outer segment length can be quantitatively assessed using Cirrus HD-OCT. Although the intrasession repeatability of PROS measurements was less than that of macular thickness measurements, the stronger correlation of PROS length with visual acuity suggests that the PROS measures may be more directly related to visual function. Photoreceptor outer segment length may be a useful physiologic outcome measure, both clinically and as a direct assessment of treatment effects.

Self-assembly of proteins into a three-dimensional multilayer system: investigation of the surface of the human fungal pathogen Aspergillus fumigatus.

PubMed

Zykwinska, Agata; Pihet, Marc; Radji, Sadia; Bouchara, Jean-Philippe; Cuenot, Stéphane

2014-06-01

Hydrophobins are small surface active proteins that fulfil a wide spectrum of functions in fungal growth and development. The human fungal pathogen Aspergillus fumigatus expresses RodA hydrophobins that self-assemble on the outer conidial surface into tightly organized nanorods known as rodlets. AFM investigation of the conidial surface allows us to evidence that RodA hydrophobins self-assemble into rodlets through bilayers. Within bilayers, hydrophilic domains of hydrophobins point inward, thus making a hydrophilic core, while hydrophobic domains point outward. AFM measurements reveal that several rodlet bilayers are present on the conidial surface thus showing that proteins self-assemble into a complex three-dimensional multilayer system. The self-assembly of RodA hydrophobins into rodlets results from attractive interactions between stacked β-sheets, which conduct to a final linear cross-β spine structure. A Monte Carlo simulation shows that anisotropic interactions are the main driving forces leading the hydrophobins to self-assemble into parallel rodlets, which are further structured in nanodomains. Taken together, these findings allow us to propose a mechanism, which conducts RodA hydrophobins to a highly ordered rodlet structure. The mechanism of hydrophobin assembly into rodlets offers new prospects for the development of more efficient strategies leading to disruption of rodlet formation allowing a rapid detection of the fungus by the immune system. Copyright © 2014 Elsevier B.V. All rights reserved.

Automatic segmentation and reconstruction of the cortex from neonatal MRI.

PubMed

Xue, Hui; Srinivasan, Latha; Jiang, Shuzhou; Rutherford, Mary; Edwards, A David; Rueckert, Daniel; Hajnal, Joseph V

2007-11-15

Segmentation and reconstruction of cortical surfaces from magnetic resonance (MR) images are more challenging for developing neonates than adults. This is mainly due to the dynamic changes in the contrast between gray matter (GM) and white matter (WM) in both T1- and T2-weighted images (T1w and T2w) during brain maturation. In particular in neonatal T2w images WM typically has higher signal intensity than GM. This causes mislabeled voxels during cortical segmentation, especially in the cortical regions of the brain and in particular at the interface between GM and cerebrospinal fluid (CSF). We propose an automatic segmentation algorithm detecting these mislabeled voxels and correcting errors caused by partial volume effects. Our results show that the proposed algorithm corrects errors in the segmentation of both GM and WM compared to the classic expectation maximization (EM) scheme. Quantitative validation against manual segmentation demonstrates good performance (the mean Dice value: 0.758+/-0.037 for GM and 0.794+/-0.078 for WM). The inner, central and outer cortical surfaces are then reconstructed using implicit surface evolution. A landmark study is performed to verify the accuracy of the reconstructed cortex (the mean surface reconstruction error: 0.73 mm for inner surface and 0.63 mm for the outer). Both segmentation and reconstruction have been tested on 25 neonates with the gestational ages ranging from approximately 27 to 45 weeks. This preliminary analysis confirms previous findings that cortical surface area and curvature increase with age, and that surface area scales to cerebral volume according to a power law, while cortical thickness is not related to age or brain growth.

Platform-Independent Cirrus and Spectralis Thickness Measurements in Eyes with Diabetic Macular Edema Using Fully Automated Software

PubMed Central

Willoughby, Alex S.; Chiu, Stephanie J.; Silverman, Rachel K.; Farsiu, Sina; Bailey, Clare; Wiley, Henry E.; Ferris, Frederick L.; Jaffe, Glenn J.

2017-01-01

Purpose We determine whether the automated segmentation software, Duke Optical Coherence Tomography Retinal Analysis Program (DOCTRAP), can measure, in a platform-independent manner, retinal thickness on Cirrus and Spectralis spectral domain optical coherence tomography (SD-OCT) images in eyes with diabetic macular edema (DME) under treatment in a clinical trial. Methods Automatic segmentation software was used to segment the internal limiting membrane (ILM), inner retinal pigment epithelium (RPE), and Bruch's membrane (BM) in SD-OCT images acquired by Cirrus and Spectralis commercial systems, from the same eye, on the same day during a clinical interventional DME trial. Mean retinal thickness differences were compared across commercial and DOCTRAP platforms using intraclass correlation (ICC) and Bland-Altman plots. Results The mean 1 mm central subfield thickness difference (standard error [SE]) comparing segmentation of Spectralis images with DOCTRAP versus HEYEX was 0.7 (0.3) μm (0.2 pixels). The corresponding values comparing segmentation of Cirrus images with DOCTRAP versus Cirrus software was 2.2 (0.7) μm. The mean 1 mm central subfield thickness difference (SE) comparing segmentation of Cirrus and Spectralis scan pairs with DOCTRAP using BM as the outer retinal boundary was −2.3 (0.9) μm compared to 2.8 (0.9) μm with inner RPE as the outer boundary. Conclusions DOCTRAP segmentation of Cirrus and Spectralis images produces validated thickness measurements that are very similar to each other, and very similar to the values generated by the corresponding commercial software in eyes with treated DME. Translational Relevance This software enables automatic total retinal thickness measurements across two OCT platforms, a process that is impractical to perform manually. PMID:28180033

Microspectrophotometric demonstration of four classes of photoreceptor in an old world primate, Macaca fascicularis.

PubMed Central

Bowmaker, J K; Dartnall, H J; Mollon, J D

1980-01-01

1. Microspectrophotometric measurements reveal four classes of photoreceptor in the retina of the cynomolgus monkey, Macaca fascicularis, which is known to possess colour vision similar to that of a normal human trichromat. 2. Although the eyes were removed in bright illumination, the densities of pigment were comparable to those we have measured in dark-adapted rhesus retinae. 3. The mean wave-lengths of peak sensitivity (lambda max) for the four classes of photoreceptor were 415, 500, 535 and 567 nm. 4. The band widths of the absorbance spectra decreased linearly as the wave-number of peak sensitivity decreased. 5. If, by assuming a reasonable value for the axial density of the rod outer segment and correcting for lens absorption, a spectral sensitivity for human vision is reconstructed from the P500 pigment, it is found to be systematically broader than the CIE scotopic sensitivity function. 6. Given explicit assumptions, it is possible from the P535 and P567 pigments to reconstruct human psychophysical sensitivities that resemble the pi 4 and pi 5 mechanisms of W. S. Stiles. 7. Although the P415 pigment has a lambda max much shorter than that of the psychophysically measured blue mechanisms, the two spectral-sensitivity functions are brought into proximity when the microspectrophotometric data are corrected for absorption by the optic media. Images Fig. 1 PMID:6767023

The osteoporosis-pseudoglioma syndrome locus is on chromosome 11q

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gong, Y.; Vikkula, M.; Boon, L.M.

The osteoporosis-pseudoglioma syndrome (OPS), is a rare autosomal recessive disorder characterized by severe osteoporosis with multiple fractures and blindness, both occurring in childhood. The precise pathogenic mechanism for OPS is unknown. Insights into its cause may be useful towards understanding the pathophysiology of more common disorders, such as senile osteoporosis, persistent hyperplasia of the primary vitreous, and retinopathy of prematurity, whose features have some similarity with OPS. As a first step in determining the cause of OPS, we have mapped the locus of the disorder to chromosome 11q. This was accomplished by assuming genetic homogeneity and by performing linkage analysismore » with homozygosity mapping in 18 individuals (7 patients, 5 unaffected siblings, and 7 parents) from 3 different consanguineous kindreds. Since the condition could be caused by an abnormal extracellular matrix component, we began by testing several candidate genes (e.g., COL1A1, COL1A2, Osteopontin, Osteonectin) distributed on 12 different chromosomes. We also initiated a systematic search at 20 cM intervals with highly polymorphic simple sequence tandem repeats. Linkage and homozygosity was detected with marker D11S913 (LOD score 3.8 at {theta} = 0). Additional markers are being tested to confirm this observation. The fibroblast collagenase, fibronectin-like-2 gene and rod outer segment protein-1 (ROM 1) also map to chromosome 11q and are candidate genes.« less

Function of MYO7A in the Human RPE and the Validity of Shaker1 Mice as a Model for Usher Syndrome 1B

PubMed Central

Gibbs, Daniel; Diemer, Tanja; Khanobdee, Kornnika; Hu, Jane; Bok, Dean

2010-01-01

Purpose. To investigate the function of MYO7A in human RPE cells and to test the validity of using shaker1 RPE in preclinical studies on therapies for Usher syndrome 1B by comparing human and mouse cells. Methods. MYO7A was localized by immunofluorescence. Primary cultures of human and mouse RPE cells were used to measure melanosome motility and rod outer segment (ROS) phagocytosis and digestion. MYO7A was knocked down in the human RPE cells by RNAi to test for a mutant phenotype in melanosome motility. Results. The distribution of MYO7A in the RPE of human and mouse was found to be comparable, both in vivo and in primary cultures. Primary cultures of human RPE cells phagocytosed and digested ROSs with kinetics comparable to that of primary cultures of mouse RPE cells. Melanosome motility was also comparable, and, after RNAi knockdown, consisted of longer-range fast movements characteristic of melanosomes in shaker1 RPE. Conclusions. The localization and function of MYO7A in human RPE cells is comparable to that in mouse RPE cells. Although shaker1 retinas do not undergo degeneration, correction of mutant phenotypes in the shaker1 RPE represents a valid preclinical test for potential therapeutic treatments. PMID:19643958

Differentiation to adipocytes in accompanied by an increase in the amounts of Gi- and Go-proteins in 3T3-L1 cells

DOE Office of Scientific and Technical Information (OSTI.GOV)

Watkins, D.C.; Northup, J.K.; Malbon, C.C.

Treatment of cultures of 3T3-L1 cells with methylisobutyl-xanthine and dexamethasone has been shown to result in accumulation of lipid and conversion to the morphology of adipocytes in more than 90% of the cells. The status of the stimulatory (Gs), inhibitory (Gi) and Go-proteins during the course of 3T3-L1 differentiation was examined. The amount of alpha subunit of Gs (..cap alpha..Gs), assayed by radiolabeling in the presence of cholera toxin and (/sup 32/P)NAD/sup +/, increased upon differentiation as previously described by others. The amounts of ..cap alpha..Gi and ..cap alpha..Go assayed by radiolabeling in the presence of pertussis toxin and (/supmore » 32/P)NAD/sup +/ increased 3-fold upon differentiation. Immunoblots of cell membranes subjected to gel electrophoresis in sodium dodecyl sulfate were probed with two rabbit antisera raised against bovine brain ..cap alpha..Go and with one raised against the..beta..-subunit of the bovine rod-outer-segment G-protein, referred to as transducin. The immunoblotting data confirm the increase upon differentiation of ..cap alpha..Go and also demonstrate an increase in the amount of the ..beta..-subunit. Thus differentiation of 3T3-L1 cells is accompanied by dramatic changes in the complexion of G-proteins in the membranes.« less

ROLES OF CELL-INTRINSIC AND MICROENVIRONMENTAL FACTORS IN PHOTORECEPTOR CELL DIFFERENTIATION

PubMed Central

Bradford, Rebecca L.; Wang, Chenwei; Zack, Donald J.; Adler, Ruben

2005-01-01

Photoreceptor differentiation requires the coordinated expression of numerous genes. It is unknown whether those genes share common regulatory mechanisms or are independently regulated by distinct mechanisms. To distinguish between these scenarios, we have used in situ hybridization, RT-PCR and real time PCR to analyze the expression of visual pigments and other photoreceptor-specific genes during chick embryo retinal development in ovo, as well as in retinal cell cultures treated with molecules that regulate the expression of particular visual pigments. In ovo, onset of gene expression was asynchronous, becoming detectable at the time of photoreceptor generation (ED 5–8) for some photoreceptor genes, but only around the time of outer segment formation (ED 14–16) for others. Treatment of retinal cell cultures with activin, staurosporine or CNTF selectively induced or down-regulated specific visual pigment genes, but many cognate rod- or cone-specific genes were not affected by the treatments. These results indicate that many photoreceptor genes are independently regulated during development, are consistent with the existence of at least two distinct stages of gene expression during photoreceptor differentiation, suggest that intrinsic, coordinated regulation of a cascade of gene expression triggered by a commitment to the photoreceptor fate is not a general mechanism of photoreceptor differentiation, and imply that using a single photoreceptor-specific “marker” as a proxy to identify photoreceptor cell fate is problematic. PMID:16120439

Melatonin Modulates Prohibitin and Cytoskeleton in the Retinal Pigment Epithelium.

PubMed

Sripathi, Srinivas R; Prigge, Cameron L; Elledge, Beth; He, Weilue; Offor, Johnpaul; Gutsaeva, Diana R; Jahng, Wan Jin

2017-07-01

The retinal pigment epithelium (RPE) plays imperative roles in normal retinal function by photoreceptor protection from light and phagocytosis of rod and cone outer segments during disc shedding. Melatonin is the free radical scavenger and circadian determinant to protect the RPE and retina from oxidative stress and regulate the circadian clock. The current study tested the hypothesis whether melatonin could affect cytoskeletal structure within RPE. Our Western blot analysis demonstrated that melatonin treatment up-regulated prohibitin 3-fold compared to control. β-tubulin levels were also up-regulated by melatonin but to a lesser extent. Initial cell shape of ARPE-19 is epitheloid, however, after 30-minute treatment with melatonin, RPE cells undergo a morphological change to a fusiform shape with spindle outgrowth. Cells return to epitheloid shape after 12 hours in untreated medium. Melatonin treated cells showed increased and dissimilar distribution of prohibitin and β-tubulin compared to non-treated cells, thus altered cytoskeletal and mitochondrial structure in the RPE. Our data implies that melatonin may play a protective role under oxidative stress, which is shown by the marker prohibitin in terms of increased expression and nuclear distribution. During the protective process, cells change their morphology. Our results suggest that melatonin treatment could be beneficial to protect mitochondria under oxidative stress and treat certain ocular diseases, including age-related macular degeneration.

Melatonin Modulates Prohibitin and Cytoskeleton in the Retinal Pigment Epithelium

PubMed Central

Sripathi, Srinivas R.; Prigge, Cameron L.; Elledge, Beth; He, Weilue; Offor, Johnpaul; Gutsaeva, Diana R.; Jahng, Wan Jin

2017-01-01

The retinal pigment epithelium (RPE) plays imperative roles in normal retinal function by photoreceptor protection from light and phagocytosis of rod and cone outer segments during disc shedding. Melatonin is the free radical scavenger and circadian determinant to protect the RPE and retina from oxidative stress and regulate the circadian clock. The current study tested the hypothesis whether melatonin could affect cytoskeletal structure within RPE. Our Western blot analysis demonstrated that melatonin treatment up-regulated prohibitin 3-fold compared to control. β-tubulin levels were also up-regulated by melatonin but to a lesser extent. Initial cell shape of ARPE-19 is epitheloid, however, after 30-minute treatment with melatonin, RPE cells undergo a morphological change to a fusiform shape with spindle outgrowth. Cells return to epitheloid shape after 12 hours in untreated medium. Melatonin treated cells showed increased and dissimilar distribution of prohibitin and β-tubulin compared to non-treated cells, thus altered cytoskeletal and mitochondrial structure in the RPE. Our data implies that melatonin may play a protective role under oxidative stress, which is shown by the marker prohibitin in terms of increased expression and nuclear distribution. During the protective process, cells change their morphology. Our results suggest that melatonin treatment could be beneficial to protect mitochondria under oxidative stress and treat certain ocular diseases, including age-related macular degeneration. PMID:28845390

Development of tissue-engineered self-expandable aortic stent grafts (Bio stent grafts) using in-body tissue architecture technology in beagles.

PubMed

Kawajiri, Hidetake; Mizuno, Takeshi; Moriwaki, Takeshi; Ishibashi-Ueda, Hatsue; Yamanami, Masashi; Kanda, Keiichi; Yaku, Hitoshi; Nakayama, Yasuhide

2015-02-01

In this study, we aimed to describe the development of tissue-engineered self-expandable aortic stent grafts (Bio stent graft) using in-body tissue architecture technology in beagles and to determine its mechanical and histological properties. The preparation mold was assembled by insertion of an acryl rod (outer diameter, 8.6 mm; length, 40 mm) into a self-expanding nitinol stent (internal diameter, 9.0 mm; length, 35 mm). The molds (n = 6) were embedded into the subcutaneous pouches of three beagles for 4 weeks. After harvesting and removing each rod, the excessive fragile tissue connected around the molds was trimmed, and thus tubular autologous connective tissues with the stent were obtained for use as Bio stent grafts (outer diameter, approximately 9.3 mm in all molds). The stent strut was completely surrounded by the dense collagenous membrane (thickness, ∼150 µm). The Bio stent graft luminal surface was extremely flat and smooth. The graft wall of the Bio stent graft possessed an elastic modulus that was almost two times higher than that of the native beagle abdominal aorta. This Bio stent graft is expected to exhibit excellent biocompatibility after being implanted in the aorta, which may reduce the risk of type 1 endoleaks or migration. © 2014 Wiley Periodicals, Inc.

Drive system for the retraction/extension of variable diameter rotor systems

NASA Technical Reports Server (NTRS)

Gmirya, Yuriy (Inventor)

2003-01-01

A drive system for a variable diameter rotor (VDR) system includes a plurality of rotor blade assemblies with inner and outer rotor blade segments. The outer blade segment being telescopically mounted to the inner blade segment. The VDR retraction/extension system includes a drive housing mounted at the root of each blade. The housing supports a spool assembly, a harmonic gear set and an electric motor. The spool assembly includes a pair of counter rotating spools each of which drive a respective cable which extends through the interior of the inboard rotor blade section and around a pulley mounted to the outboard rotor blade section. In operation, the electric motor drives the harmonic gear set which rotates the counter rotating spools. Rotation of the spools causes the cables to be wound onto or off their respective spool consequently effecting retraction/extension of the pulley and the attached outboard rotor blade section relative the inboard rotor blade section. As each blade drive system is independently driven by a separate electrical motor, each independent VDR blade assembly is independently positionable.

Retinal degeneration in cats fed casein. IV. The early receptor potential.

PubMed

Berson, E L; Watson, G; Grasse, K L; Szamier, R B

1981-08-01

Electroretinographic studies of casein-fed cats with retinal taurine deficiency revealed that the early receptor potential (ERP) was initially normal in amplitude at a time when the a-wave and b-wave of the electroretinogram were substantially reduced or even nondetectable. The preserved ERP's in these taurine-deficient cats could be correlated with the histologic finding that their outer segments were relatively intact over 90% of the retinal area subtended by the test flash. The sequence of electroretinographic changes in these taurine-deficient cats was also consistent with previous biochemical studies on the normal cat retina that have shown a relatively low concentration of taurine at the level of the outer segments and a higher concentration at the level of the inner segments. The responses in early stages from taurine-deficient cats differed from the responses obtained from vitamin A--deficient cats but resembled those from cats that received an intravitreal injection of ouabain. Similarities and a difference between the responses of taurine-deficient cats and those of patients with early retinitis pigmentosa are considered.

Rhodopsin expression in the zebrafish pineal gland from larval to adult stage.

PubMed

Magnoli, Domenico; Zichichi, Rosalia; Laurà, Rosaria; Guerrera, Maria Cristina; Campo, Salvatore; de Carlos, Felix; Suárez, Alberto Álvarez; Abbate, Francesco; Ciriaco, Emilia; Vega, Jose Antonio; Germanà, Antonino

2012-03-09

The zebrafish pineal gland plays an important role in different physiological functions including the regulation of the circadian clock. In the fish pineal gland the pinealocytes are made up of different segments: outer segment, inner segment and basal pole. Particularly, in the outer segment the rhodopsin participates in the external environment light reception that represents the first biochemical step in the melatonin production. It is well known that the rhodopsin in the adult zebrafish is well expressed in the pineal gland but both the expression and the cellular localization of this protein during development remain still unclear. In this study using qRT-PCR, sequencing and immunohistochemistry the expression as well as the protein localization of the rhodopsin in the zebrafish from larval (10 dpf) to adult stage (90 dpf) were demonstrated. The rhodopsin mRNA expression presents a peak of expression at 10 dpf, a further reduction to 50 dpf before increasing again in the adult stage. Moreover, the cellular localization of the rhodopsin-like protein was always localized in the pinealocyte at all ages examined. Our results demonstrated the involvement of the rhodopsin in the zebrafish pineal gland physiology particularly in the light capture during the zebrafish lifespan. Copyright © 2012 Elsevier B.V. All rights reserved.

Element for use in an inductive coupler for downhole components

DOEpatents

Hall, David R [Provo, UT; Fox, Joe [Spanish Fork, UT

2009-03-31

An element for use in an inductive coupler for downhole components comprises an annular housing having a generally circular recess. The element further comprises a plurality of generally linear, magnetically conductive segments. Each segment includes a bottom portion, an inner wall portion, and an outer wall portion. The portions together define a generally linear trough from a first end to a second end of each segment. The segments are arranged adjacent to each other within the housing recess to form a generally circular trough. The ends of at least half of the segments are shaped such that the first end of one of the segments is complementary in form to the second end of an adjacent segment. In one embodiment, all of the ends are angled. Preferably, the first ends are angled with the same angle and the second ends are angled with the complementary angle.

Learning-based automated segmentation of the carotid artery vessel wall in dual-sequence MRI using subdivision surface fitting.

PubMed

Gao, Shan; van 't Klooster, Ronald; Kitslaar, Pieter H; Coolen, Bram F; van den Berg, Alexandra M; Smits, Loek P; Shahzad, Rahil; Shamonin, Denis P; de Koning, Patrick J H; Nederveen, Aart J; van der Geest, Rob J

2017-10-01

The quantification of vessel wall morphology and plaque burden requires vessel segmentation, which is generally performed by manual delineations. The purpose of our work is to develop and evaluate a new 3D model-based approach for carotid artery wall segmentation from dual-sequence MRI. The proposed method segments the lumen and outer wall surfaces including the bifurcation region by fitting a subdivision surface constructed hierarchical-tree model to the image data. In particular, a hybrid segmentation which combines deformable model fitting with boundary classification was applied to extract the lumen surface. The 3D model ensures the correct shape and topology of the carotid artery, while the boundary classification uses combined image information of 3D TOF-MRA and 3D BB-MRI to promote accurate delineation of the lumen boundaries. The proposed algorithm was validated on 25 subjects (48 arteries) including both healthy volunteers and atherosclerotic patients with 30% to 70% carotid stenosis. For both lumen and outer wall border detection, our result shows good agreement between manually and automatically determined contours, with contour-to-contour distance less than 1 pixel as well as Dice overlap greater than 0.87 at all different carotid artery sections. The presented 3D segmentation technique has demonstrated the capability of providing vessel wall delineation for 3D carotid MRI data with high accuracy and limited user interaction. This brings benefits to large-scale patient studies for assessing the effect of pharmacological treatment of atherosclerosis by reducing image analysis time and bias between human observers. © 2017 American Association of Physicists in Medicine.

Segmentation of the common carotid artery with active shape models from 3D ultrasound images

NASA Astrophysics Data System (ADS)

Yang, Xin; Jin, Jiaoying; He, Wanji; Yuchi, Ming; Ding, Mingyue

2012-03-01

Carotid atherosclerosis is a major cause of stroke, a leading cause of death and disability. In this paper, we develop and evaluate a new segmentation method for outlining both lumen and adventitia (inner and outer walls) of common carotid artery (CCA) from three-dimensional ultrasound (3D US) images for carotid atherosclerosis diagnosis and evaluation. The data set consists of sixty-eight, 17× 2× 2, 3D US volume data acquired from the left and right carotid arteries of seventeen patients (eight treated with 80mg atorvastain and nine with placebo), who had carotid stenosis of 60% or more, at baseline and after three months of treatment. We investigate the use of Active Shape Models (ASMs) to segment CCA inner and outer walls after statin therapy. The proposed method was evaluated with respect to expert manually outlined boundaries as a surrogate for ground truth. For the lumen and adventitia segmentations, respectively, the algorithm yielded Dice Similarity Coefficient (DSC) of 93.6%+/- 2.6%, 91.8%+/- 3.5%, mean absolute distances (MAD) of 0.28+/- 0.17mm and 0.34 +/- 0.19mm, maximum absolute distances (MAXD) of 0.87 +/- 0.37mm and 0.74 +/- 0.49mm. The proposed algorithm took 4.4 +/- 0.6min to segment a single 3D US images, compared to 11.7+/-1.2min for manual segmentation. Therefore, the method would promote the translation of carotid 3D US to clinical care for the fast, safety and economical monitoring of the atherosclerotic disease progression and regression during therapy.

Light-induced migration of retinal microglia into the subretinal space.

PubMed

Ng, T F; Streilein, J W

2001-12-01

To explore the effects of light exposure and deprivation on the distribution and function of microglia in the subretinal space of mice. Using a monoclonal antibody, 5D4, that identifies resting, ramified microglia, the distribution and density of microglia in the retina, and the subretinal space were determined by confocal microscopy and by immunohistochemistry of cryopreserved sections of eyes of albino and pigmented mice exposed to diverse levels of light, ranging from complete darkness to intense brightness. Axotomized retinal ganglion cells were retrograde labeled by fluorescent tracer to determine whether the marker colocalizes to 5D4+ cells. Electron microscopy was used to evaluate microglia for evidence of phagocytosis. 5D4+ microglia in pigmented eyes were limited to the inner retinal layers, but in albino eyes 5D4+ cells were found in the outer retinal layers and subretinal space as well. The subretinal space of eyes of albino mice raised from birth in complete darkness contained few 5D4+ cells, but exposure to light caused the rapid accumulation of 5D4+ cells at this site. 5D4+ cell density in the subretinal space correlated directly with intensity of ambient light. Retrograde labeling of axotomized ganglion cells resulted in 5D4+ cells in the subretinal space that contained the retrograde label. Subretinal microglia contained phagocytized rod outer segment discs. On intense light exposure, 5D4+ cells adopted an active morphology, but failed to express class II major histocompatibility complex (MHC) molecules. Light exposure induced retinal microglia migration into the subretinal space in albino mice. Subretinal microglia appeared to augment through phagocytosis the capacity of pigment epithelium to take up the photoreceptor debris of light toxicity. The unexpected presence of these cells in the subretinal space raises questions concerning their potential contribution to immune privilege in this space and to the fate of retinal transplants.

Biomechanical Evaluation of a Growth-Friendly Rod Construct.

PubMed

Galvis, Sarah; Arnold, Josh; Mannen, Erin; Wong, Benjamin; Sis, Hadley; Cadel, Eileen; Anderson, John; Anderson, Dennis; Arnold, Paul; Friis, Elizabeth

2017-01-01

Distraction-type rods mechanically stabilize the thorax and improve lung growth and function by applying distraction forces at the rib, spine, pelvis, or a combination of locations. However, the amount of stability the rods provide and the amount the thorax needs is unknown. Five freshly frozen and thawed cadaveric thoracic spine specimens were tested for lateral bending, flexion/extension, and axial rotation in displacement control (1°/sec) to a load limit of ±5 Nm for five cycles after which a growth-friendly unilateral rod was placed in a simulated rib-to-lumbar attachment along the right side. The specimens were tested again in the same modes of bending. From the seven Optotrak Orthopedic Research Pin markers (Northern Digital Inc., Waterloo, Ontario, Canada) inserted into the top potting to denote T1, and the right pedicles at T2, T4, T5, T8, T9, and T11 and the Standard Needle Tip Pressure Transducers (Gaeltech, Isle of Skye, Scotland) inserted into the T4/T5 and T8/T9 discs, motion, stiffness, and pressure data were calculated. Parameters from the third cycle of the intact case and the construct case were compared using two-tailed paired t tests with 0.05 as the level of significance. With the construct attached, the T1-T4 segment showed a 30% increase in neutral zone stiffness during extension (p = .001); the T8-T12 segment experienced a 63% reduction in the in-plane range of motion during flexion (p = .04); and the T8/T9 spinal motion unit had a significant decrease of 24% in elastic zone stiffness during left axial rotation (p = .04). It is clear the device as tested here does not produce large biomechanical changes, but the balance between providing desired changes while preventing complications remains difficult. Copyright © 2016 Scoliosis Research Society. Published by Elsevier Inc. All rights reserved.

Spent fuel behavior under abnormal thermal transients during dry storage

DOE Office of Scientific and Technical Information (OSTI.GOV)

Stahl, D.; Landow, M.P.; Burian, R.J.

1986-01-01

This study was performed to determine the effects of abnormally high temperatures on spent fuel behavior. Prior to testing, calculations using the CIRFI3 code were used to determine the steady-state fuel and cask component temperatures. The TRUMP code was used to determine transient heating rates under postulated abnormal events during which convection cooling of the cask surfaces was obstructed by a debris bed covering the cask. The peak rate of temperature rise during the first 6 h was calculated to be about 15/sup 0/C/h, followed by a rate of about 1/sup 0/C/h. A Turkey Point spent fuel rod segment wasmore » heated to approx. 800/sup 0/C. The segment deformed uniformly with an average strain of 17% at failure and a local strain of 60%. Pretest characterization of the spent fuel consisted of visual examination, profilometry, eddy-current examination, gamma scanning, fission gas collection, void volume measurement, fission gas analysis, hydrogen analysis of the cladding, burnup analysis, cladding metallography, and fuel ceramography. Post-test characterization showed that the failure was a pinhole cladding breach. The results of the tests showed that spent fuel temperatures in excess of 700/sup 0/C are required to produce a cladding breach in fuel rods pressurized to 500 psing (3.45 MPa) under postulated abnormal thermal transient cask conditions. The pinhole cladding breach that developed would be too small to compromise the confinement of spent fuel particles during an abnormal event or after normal cooling conditions are restored. This behavior is similar to that found in other slow ramp tests with irradiated and nonirradiated rod sections and nonirradiated whole rods under conditions that bracketed postulated abnormal heating rates. This similarity is attributed to annealing of the irradiation-strengthened Zircaloy cladding during heating. In both cases, the failure was a benign, ductile pinhole rupture.« less

Spectral domain optical coherence tomography findings in tamoxifen retinopathy--a case report.

PubMed

Nair, Sandhya Narayanan; Anantharaman, Giridhar; Gopalakrishnan, Mahesh; Vyas, Jyothiprakash

2013-01-01

To report spectral domain optical coherence tomography findings in a case of typical tamoxifen retinopathy. In this observational case report, a patient with tamoxifen retinopathy was imaged with spectral domain optical coherence tomography and fundus auto fluorescence. Spectral domain optical coherence tomography showed numerous hyperreflective spots within the retina, mainly in the inner retinal layers in both the eyes. The external limiting membrane, the Inner Segment-Outer Segment junction, and the photoreceptors were not discernable at the fovea in the right eye. In the left eye, there was foveal atrophy with total loss of photoreceptors. The autofluorescent images showed macular hypofluorescence with foveal hyperfluorescence. Spectral domain optical coherence tomography demonstrated abnormalities in the outer retinal layers in tamoxifen retinopathy. There were also characteristic alterations in the autofluorescence pattern at the macula in tamoxifen retinopathy.

Assembly of Nanorods into Designer Superstructures: The Role of Templating, Capillary Forces, Adhesion, and Polymer Hydration

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ciszek, Jacob W.; Huang, Ling; Tsonchev, Stefan

The assembly mechanism by which hundreds of thousands of two-segment gold-polypyrrole nanorods are assembled into kinetically controlled shape-directed superstructures is examined to predict the range of nanoparticle sizes and materials that can be utilized in their formation. Four processes are responsible for assembly: templating, capillary force assembly, adhesion, and polymer hydration. It is shown that templating, where rods are prepositioned for assembly, is scale invariant and that the energy-minimized state after this step is highly disordered. In addition, we predict that superstructures can be made independently from patterns of rods separated by a distance as small as six times themore » inter-rod spacing. Both modeling and experiment show that adhesion and polymer dehydration, which induces curvature in the superstructures, are applicable to other materials. However, the high surface energy and low elastic modulus of polypyrrole are advantageous toward generating three-dimensional structures, inducing curvature at gold/polypyrrole length ratios as large as 7:1.« less

Visual probes and methods for placing visual probes into subsurface areas

DOEpatents

Clark, Don T.; Erickson, Eugene E.; Casper, William L.; Everett, David M.

2004-11-23

Visual probes and methods for placing visual probes into subsurface areas in either contaminated or non-contaminated sites are described. In one implementation, the method includes driving at least a portion of a visual probe into the ground using direct push, sonic drilling, or a combination of direct push and sonic drilling. Such is accomplished without providing an open pathway for contaminants or fugitive gases to reach the surface. According to one implementation, the invention includes an entry segment configured for insertion into the ground or through difficult materials (e.g., concrete, steel, asphalt, metals, or items associated with waste), at least one extension segment configured to selectively couple with the entry segment, at least one push rod, and a pressure cap. Additional implementations are contemplated.