Review lecture: Apposition eyes of large diurnal insects as organs adapted to seeing

1980 ◽  
Vol 207 (1168) ◽  
pp. 287-309 ◽  
Keyword(s):  
Nodal Point ◽  
Visual Fields ◽  
Photoreceptor Cells ◽  
Resolving Power ◽  
Field Size ◽  
Correct Position ◽  
Anatomical Arrangement ◽  
Angular Coordinates ◽  
And Function ◽  
Facet Size

(1) The fields of view of the photoreceptor cells are determined by the dimensions and anatomical arrangement of the optical part of the ommatidium. The dimensions, and therefore the fields of view of the ommatidia are also related across the eye. In the relation between structure and function there are many points that invite discussion, but the intention is to order our knowledge so that the gaps become obvious. (2) The first step has been to make maps of the eyes showing the maximum theoretical resolving power of the facets and also the interommatidial angle, the reciprocal of which is the maximum spatial resolution of combinations of facets. The ratio of these two resolutions at each point shows the minimum overlap of the visual fields. These maps can be made from the outside of the eye; they show the main types of eye. (3) The next step is to work out the optics of individual ommatidia so that the focal lengths and receptor widths can be measured. The field width can then be predicted from the facet size and the subtense of the receptor at the posterior nodal point. The final step is to measure the field widths of individual ommatidia experimentally as a test of the optical theory, and to make maps of the actual fields in their correct position on the eye in angular coordinates. (4) Three examples of maps of actual fields are given, and their anato­mical and diffraction components are separated. The maps are an essential step towards the electrophysiological analysis of the ganglia behind the eye. A theory of the origin of the fields in terms of anatomy and optics also opens the way to an analysis of mechanisms that change the field size upon adaptation to light. A comparative study of the fields in different eye regions and in different species can also be related to visual habits and behaviour.

Anatomy of the Regional Differences in the Eye of the Mantis Ciulfina

1979 ◽  
Vol 80 (1) ◽  
pp. 165-190 ◽  
Author(s):  
G. A. HORRIDGE ◽  
PETER DUELLI
Keyword(s):  
Regional Differences ◽  
Compound Eye ◽  
Focal Length ◽  
Visual Fields ◽  
Resolving Power ◽  
Acceptance Angle ◽  
Extended Source ◽  
Angular Coordinates ◽  
The Individual ◽  
Different Parts

In the compound eye of Ciulfina (Mantidae) there are large regional differences in interommatidial angle as measured optically from the pseudopupil. Notably there is an acute zone which looks backwards as well as one looking forwards. There are correlated regional differences in the dimensions of the ommatidia. The following anatomical features which influence the optical performance have been measured in different parts of the eye The facet diameter is greater where the interommatidial angle is smaller. This could influence resolving power, but calculation shows that facet size does not exert a dominant effect on the visual fields of the receptors. The rhabdom tip diameter, which theoretically has a strong influence on the size of visual fields, is narrower in eye regions where the interommatidial angle is smaller. The cone length, from which the focal length can be estimated, is greater where the interommatidial angle is smaller. Estimation of the amount of light reaching the rhabdom suggests that different parts of the eye have similar sensitivity to a point source of light, but differ by a factor of at least 10 in sensitivity to an extended source. There is anatomical evidence that in the acute zone the sensitivity has been sacrificed for the sake of resolution. Maps of the theoretical minimum fields of the photoreceptors, plotted in their positions on the eye in angular coordinates, suggest that there are too few ommatidia for the eye as a whole to reconstruct all the visual detail that the individual receptors can resolve. The conclusion from (3) and (4), together with some behavioural evidence, suggests that the eye structure must make possible the resolution of small movements of contrasting edges and of small dark contrasting objects but there is less emphasis on the total reconstruction of fine patterns because the interommatidial angle is greater than the estimate of the acceptance angle.

Scanning tunneling microscopy (STM) of DNA and RNA

1989 ◽  
Vol 47 ◽  
pp. 34-35
Author(s):  
Patricia G. Arscott ◽  
Gil Lee ◽  
Victor A. Bloomfield ◽  
D. Fennell Evans
Keyword(s):  
Molecular Structures ◽  
Inorganic Materials ◽  
Resolving Power ◽  
Scanning Tunneling ◽  
Tunneling Microscopy ◽  
Form And Function ◽  
Dna And Rna ◽  
Calf Thymus ◽  
And Function ◽  
The Relationship

STM is one of the most promising techniques available for visualizing the fine details of biomolecular structure. It has been used to map the surface topography of inorganic materials in atomic dimensions, and thus has the resolving power not only to determine the conformation of small molecules but to distinguish site-specific features within a molecule. That level of detail is of critical importance in understanding the relationship between form and function in biological systems. The size, shape, and accessibility of molecular structures can be determined much more accurately by STM than by electron microscopy since no staining, shadowing or labeling with heavy metals is required, and there is no exposure to damaging radiation by electrons. Crystallography and most other physical techniques do not give information about individual molecules.We have obtained striking images of DNA and RNA, using calf thymus DNA and two synthetic polynucleotides, poly(dG-me5dC)·poly(dG-me5dC) and poly(rA)·poly(rU).

The variation of resolution and of ommatidial dimensions in the compound eyes of the fiddler crab Uca lactea annulipes (Ocypodidae, Brachyura, Decapoda)

1996 ◽  
Vol 199 (7) ◽  
pp. 1569-1577 ◽  
Author(s):  
J Zeil ◽  
M Al-Mutairi
Keyword(s):  
Visual Field ◽  
Fiddler Crab ◽  
Visual Fields ◽  
Horizontal Resolution ◽  
Resolving Power ◽  
Compound Eyes ◽  
Vertical Resolution ◽  
Histological Techniques ◽  
Uca Lactea

We studied variations in the optical properties of the compound eyes of Uca lactea annulipes using in vivo optical and histological techniques. The distribution of resolving power in the eyes of this fiddler crab species is typical for arthropods that inhabit flat environments: the eyes possess a panoramic equatorial acute zone for vertical resolution and a steep decrease of resolution away from the eye equator in the dorsal and ventral visual fields. The dimensions of the cellular components of the ommatidia vary accordingly: in the equatorial part of the eyes, facets are larger, and crystalline cones and rhabdoms are longer than in the dorsal and ventral parts of the eyes. Along the eye equator, horizontal resolution is low compared with vertical resolution and varies little throughout the visual field. The eyes of Uca lactea annulipes are unusual in that the gradient of vertical anatomical and optical resolution is steeper in the dorsal than in the ventral visual field. We interpret this difference as indicating that the information content of the world as seen by the crabs differs above and below the horizon line in specific and predictable ways.

scholarly journals Custom extraction of macular ganglion cell-inner plexiform layer thickness more precisely co-localizes structural measurements with visual fields test grids

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Janelle Tong ◽  
David Alonso-Caneiro ◽  
Nayuta Yoshioka ◽  
Michael Kalloniatis ◽  
Barbara Zangerl
Keyword(s):  
Ganglion Cell ◽  
Optic Disc ◽  
Visual Fields ◽  
Plexiform Layer ◽  
Inner Plexiform Layer ◽  
Spatial Direction ◽  
Healthy Cohort ◽  
Foveal Center ◽  
And Function ◽  
Thickness Measurements

Abstract We aimed to evaluate methods of extracting optical coherence tomography (OCT)-derived macular ganglion cell-inner plexiform layer (GCIPL) thickness measurements over retinal locations corresponding to standard visual field (VF) test grids. A custom algorithm was developed to automatically extract GCIPL thickness measurements from locations corresponding to Humphrey Field Analyser 10-2 and 30-2 test grids over Goldmann II, III and V stimulus sizes from a healthy cohort of 478 participants. Differences between GCIPL thickness measurements based on VF test grids (VF-based paradigms) and the 8 × 8 grid, as per instrument review software, were analyzed, as were impacts of fovea to optic disc tilt and areas over which GCIPL thickness measurements were extracted. Significant differences between the VF-based paradigms and the 8 × 8 grid were observed at up to 55% of locations across the macula, with the greatest deviations at the fovea (median 25.5 μm, 95% CI 25.24–25.72 μm, P < .0001). While significant correlations with fovea to optic disc tilt were noted at up to 33% of locations distributed 6°–8° from the foveal center, there were no marked differences in GCIPL thickness measurements between VF-based paradigms using different stimulus sizes. As such, standard high-density OCT measurement paradigms do not adequately reflect GCIPL measurements at retinal locations tested with standard VF patterns, with the central macular region contributing most to the observed differences and with further correction required for fovea to optic disc tilt. Spatial direction of GCIPL thickness measurements will improve future comparisons of structure and function, thereby improving methods designed to detect pathology affecting the inner retina.

Retinal Topography in Two Species of Baleen Whale (Cetacea: Mysticeti)

2018 ◽  
Vol 92 (3-4) ◽  
pp. 97-116 ◽  
Author(s):  
Thomas J. Lisney ◽  
Shaun P. Collin
Keyword(s):  
Ganglion Cells ◽  
Feeding Strategy ◽  
Visual Fields ◽  
Humpback Whale ◽  
High Density ◽  
Resolving Power ◽  
Temporal Area ◽  
Baleen Whales ◽  
Axial Diameter ◽  
Retinal Topography

Little is known about the visual systems of large baleen whales (Mysticeti: Cetacea). In this study, we investigate eye morphology and the topographic distribution of retinal ganglion cells (RGCs) in two species of mysticete, Bryde’s whale (Balaenoptera edeni) and the humpback whale (Megaptera novaeanglia). Both species have large eyes characterised by a thickened cornea, a heavily thickened sclera, a highly vascularised fibro-adipose bundle surrounding the optic nerve at the back of the eye, and a reflective blue-green tapetum fibrosum. Using stereology and retinal whole mounts, we estimate a total of 274,268 and 161,371 RGCs in the Bryde’s whale and humpback whale retinas, respectively. Both species have a similar retinal topography, consisting of nasal and temporal areas of high RGC density, suggesting that having higher visual acuity in the anterior and latero-caudal visual fields is particularly important in these animals. The temporal area is larger in both species and contains the peak RGC densities (160 cells mm–2 in the humpback whale and 200 cells mm–2 in Bryde’s whale). In the Bryde’s whale retina, the two high-density areas are connected by a weak centro-ventral visual streak, but such a specialisation is not evident in the humpback whale. Measurements of RGC soma area reveal that although the RGCs in both species vary substantially in size, RGC soma area is inversely proportional to RGC density, with cells in the nasal and temporal high-density areas being relatively more homogeneous in size compared to the RGCs in the central retina and the dorsal and ventral retinal periphery. Some of the RGCs were very large, with soma areas of over 2,000 µm2. Using peak RGC density and eye axial diameter (Bryde’s whale: 63.5 mm; humpback whale: 48.5 mm), we estimated the peak anatomical spatial resolving power in water to be 4.8 cycles/degree and 3.3 cycles/degree in the Bryde’s whale and the humpback whale, respectively. Overall, our findings for these two species are very similar to those reported for other species of cetaceans. This indicates that, irrespective of the significant differences in body size and shape, behavioural ecology and feeding strategy between mysticetes and odontocetes (toothed whales), cetacean eyes are adapted to vision in dim light and adhere to a common “bauplan” that evolved prior to the divergence of the two cetacean parvorders (Odontoceti and Mysticeti) over 30 million years ago.

scholarly journals Dysfunction of Heterotrimeric Kinesin-2 in Rod Photoreceptor Cells and the Role of Opsin Mislocalization in Rapid Cell Death

2010 ◽  
Vol 21 (23) ◽  
pp. 4076-4088 ◽  
Author(s):  
Vanda S. Lopes ◽  
David Jimeno ◽  
Kornnika Khanobdee ◽  
Xiaodan Song ◽  
Bryan Chen ◽  
...  
Keyword(s):  
Cell Death ◽  
Outer Segment ◽  
Photoreceptor Cell ◽  
Photoreceptor Cells ◽  
Cell Loss ◽  
Rod Photoreceptor ◽  
Retinal Degenerations ◽  
Cell Counts ◽  
And Function

Due to extensive elaboration of the photoreceptor cilium to form the outer segment, axonemal transport (IFT) in photoreceptors is extraordinarily busy, and retinal degeneration is a component of many ciliopathies. Functional loss of heterotrimeric kinesin-2, a major anterograde IFT motor, causes mislocalized opsin, followed by rapid cell death. Here, we have analyzed the nature of protein mislocalization and the requirements for the death of kinesin-2-mutant rod photoreceptors. Quantitative immuno EM showed that opsin accumulates initially within the inner segment, and then in the plasma membrane. The light-activated movement of arrestin to the outer segment is also impaired, but this defect likely results secondarily from binding to mislocalized opsin. Unlike some other retinal degenerations, neither opsin–arrestin complexes nor photoactivation were necessary for cell loss. In contrast, reduced rod opsin expression provided enhanced rod and cone photoreceptor survival and function, as measured by photoreceptor cell counts, apoptosis assays, and ERG analysis. The cell death incurred by loss of kinesin-2 function was almost completely negated by Rho−/−. Our results indicate that mislocalization of opsin is a major cause of photoreceptor cell death from kinesin-2 dysfunction and demonstrate the importance of accumulating mislocalized protein per se, rather than specific signaling properties of opsin, stemming from photoactivation or arrestin binding.

scholarly journals LRIT3 is required for nyctalopin expression and normal ON and OFF pathway signaling in the retina

2018 ◽  
Author(s):  
Nazarul Hasan ◽  
Gobinda Pangeni ◽  
Thomas A. Ray ◽  
Kathryn M. Fransen ◽  
Jennifer Noel ◽  
...  
Keyword(s):  
Visual Function ◽  
Metabotropic Glutamate Receptor ◽  
Glutamate Release ◽  
Electrode Array ◽  
Light Response ◽  
Photoreceptor Cells ◽  
Sole Source ◽  
Bipolar Cells ◽  
Metabotropic Glutamate ◽  
And Function

ABSTRACTAt its first synapse, the retina establishes two parallel channels that encode light increments (ON) or decrements (OFF). At the same synapse, changes in photoreceptor glutamate release are sensed by ON bipolar cells (BCs) via the metabotropic glutamate receptor 6 (mGluR6), and OFF BCs via ionotropic BCs, which differ in their synaptic configuration with the photoreceptor terminal. ON BCs form invaginating synapses that bring them in close proximity to presynaptic ribbons and the presumed sole source of glutamate release. OFF bipolar cells form flat contacts distal to the ribbon synapse. We investigated the role of LRIT3 in normal assembly and function of the mGlur6 signaling cascade present in ON BCs. We demonstrate that LRIT3 is required for nyctalopin expression and thus TRPM1 expression and function. Using glutamate imaging, whole-cell electrophysiology, and multi-electrode array extracellular recordings we demonstrate that the loss of LRIT3 impacts both the ON and OFF pathways at the level of the BCs. The effect on ON pathway signaling, a lack of ON BC response, is shared by mutants lacking mGluR6, TRPM1 GPR179 or nyctalopin. The effects on the OFF pathway are unique to LRIT3, and include a decrease in response amplitude of both OFF BC and GCs. Based on these results, we propose a working model where LRIT3 is required for either efficient glutamate release or reuptake from the first retinal synapse.SIGNIFICANCE STATEMENTAt the first visual synapse, photoreceptor cells signal to two distinct bipolar cell (BC) populations, one characterized by a depolarizing response to light onset (ON or DBCs), the other by a hyperpolarizing response (OFF or HBCs). The DBC light response depends on a G protein-coupled receptor and associated protein complex, known as the signalplex. Mutations in signalplex proteins lead to DBC pathway-specific loss of visual function. Here we show how loss of LRIT3, a previously identified signalplex protein, prevents functional assembly of the DBC signalplex and alters visual function in both ON and OFF signaling pathways. Thus, our results indicate that the function of LRIT3 at this first synapse extends beyond assembly of the DBC signalplex.

scholarly journals Sophisticated Gene Regulation for a Complex Physiological System: The Role of Non-coding RNAs in Photoreceptor Cells

2021 ◽  
Vol 8 ◽  
Author(s):  
Sabrina Carrella ◽  
Sandro Banfi ◽  
Marianthi Karali
Keyword(s):  
Molecular Mechanisms ◽  
Developmental Process ◽  
Photoreceptor Cells ◽  
Sensory Transduction ◽  
Circular Rnas ◽  
Therapeutic Implications ◽  
Physiological Processes ◽  
Non Coding Rnas ◽  
And Function

Photoreceptors (PRs) are specialized neuroepithelial cells of the retina responsible for sensory transduction of light stimuli. In the highly structured vertebrate retina, PRs have a highly polarized modular structure to accommodate the demanding processes of phototransduction and the visual cycle. Because of their function, PRs are exposed to continuous cellular stress. PRs are therefore under pressure to maintain their function in defiance of constant environmental perturbation, besides being part of a highly sophisticated developmental process. All this translates into the need for tightly regulated and responsive molecular mechanisms that can reinforce transcriptional programs. It is commonly accepted that regulatory non-coding RNAs (ncRNAs), and in particular microRNAs (miRNAs), are not only involved but indeed central in conferring robustness and accuracy to developmental and physiological processes. Here we integrate recent findings on the role of regulatory ncRNAs (e.g., miRNAs, lncRNAs, circular RNAs, and antisense RNAs), and of their contribution to PR pathophysiology. We also outline the therapeutic implications of translational studies that harness ncRNAs to prevent PR degeneration and promote their survival and function.

scholarly journals Prominins control ciliary length throughout the animal kingdom: New lessons from human prominin-1 and zebrafish prominin-3

2020 ◽  
Vol 295 (18) ◽  
pp. 6007-6022 ◽  
Author(s):  
József Jászai ◽  
Kristina Thamm ◽  
Jana Karbanová ◽  
Peggy Janich ◽  
Christine A. Fargeas ◽  
...  
Keyword(s):  
Primary Cilia ◽  
Photoreceptor Cells ◽  
Dominant Negative ◽  
Dominant Negative Mutant ◽  
Loss Of Function ◽  
Animal Kingdom ◽  
Left Right Asymmetry ◽  
And Function ◽  
The Impact

Prominins (proms) are transmembrane glycoproteins conserved throughout the animal kingdom. They are associated with plasma membrane protrusions, such as primary cilia, as well as extracellular vesicles derived thereof. Primary cilia host numerous signaling pathways affected in diseases known as ciliopathies. Human PROM1 (CD133) is detected in both somatic and cancer stem cells and is also expressed in terminally differentiated epithelial and photoreceptor cells. Genetic mutations in the PROM1 gene result in retinal degeneration by impairing the proper formation of the outer segment of photoreceptors, a modified cilium. Here, we investigated the impact of proms on two distinct examples of ciliogenesis. First, we demonstrate that the overexpression of a dominant-negative mutant variant of human PROM1 (i.e. mutation Y819F/Y828F) significantly decreases ciliary length in Madin–Darby canine kidney cells. These results contrast strongly to the previously observed enhancing effect of WT PROM1 on ciliary length. Mechanistically, the mutation impeded the interaction of PROM1 with ADP-ribosylation factor–like protein 13B, a key regulator of ciliary length. Second, we observed that in vivo knockdown of prom3 in zebrafish alters the number and length of monocilia in the Kupffer's vesicle, resulting in molecular and anatomical defects in the left-right asymmetry. These distinct loss-of-function approaches in two biological systems reveal that prom proteins are critical for the integrity and function of cilia. Our data provide new insights into ciliogenesis and might be of particular interest for investigations of the etiologies of ciliopathies.

Developmental patterns of protein expression in photoreceptors implicate distinct environmental versus cell-intrinsic mechanisms

2001 ◽  
Vol 18 (1) ◽  
pp. 157-168 ◽  
Author(s):  
P.T. JOHNSON ◽  
R.R. WILLIAMS ◽  
B.E. REESE
Keyword(s):  
Expression Patterns ◽  
Photoreceptor Cells ◽  
Primary Role ◽  
Spatial And Temporal Patterns ◽  
Photoreceptor Outer Segments ◽  
Outer Segments ◽  
Cone Opsin ◽  
Rhodopsin Kinase ◽  
Spatio Temporal ◽  
And Function

The present study has examined the spatial and temporal expression patterns of various proteins associated with the structure and function of mature photoreceptor outer segments in the developing ferret's retina using immunocytochemistry and RT-PCR. One set of proteins, including rod opsin, arrestin, and recoverin, was detected progressively in photoreceptors as they became postmitotic, being expressed well before the differentiation of outer segments. A second set of proteins, including β- and γ-transducin, cGMP-phosphodiesterase, phosducin, rhodopsin kinase, rod cGMP-gated cation channel protein, and peripherin, displayed a contrasting temporal onset and pattern of spatial emergence. These latter proteins first became detectable either shortly before or coincident with outer segment formation, and were expressed simultaneously in both older and younger photoreceptor cells. A third set, the short wavelength-sensitive (SWS) and medium wavelength-sensitive (MWS) cone opsin proteins, was the last to be detected, but materialized in a spatio-temporal pattern reminiscent of the neurogenetic gradient of the cones. These different spatial and temporal patterns indicate that cellular maturation must play a primary role in regulating the onset of expression of some of these proteins, while extrinsic signals must act to coordinate the expression of other proteins across photoreceptors of different ages.

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