DigitalUM :: Browsing by Subject "Photoreceptors"

Browsing by Subject "Photoreceptors"

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Open Access
Fine structure of the retinal photoreceptors of the great horned owl (Bubo virginianus)
(Murcia : F. Hernández, 1993) Braekevelt, Charlie R.
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 no hyperboloid of glycogen. Single cones show a slightly tapered outer segment, a heterogeneous 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 externa1 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 noctumally active bird than is usually noted in avian species.
Open Access
Fine structure of the retinal photoreceptors of the tiger salamander (Ambystoma tigrinum)
(F. Hernández y Juan F. Madrid. Universidad de Murcia: Departamento de Biología Celular e Histología, 1993) Braekevelt, C. R.
The retinal photoreceptors of the tiger salamander (Ambystoma tigrinum) have been studied by light and electron microscopy in both light- and dark-adaptation. Rods and cones are present in this duplex retina in a ratio of about 20:1. As in other urodele species these photoreceptors are very large cells. The rod outer segment is composed of bi-membranous discs of uniform diameter displaying several very deep incisures. The rod inner segment displays an ellipsoid of mitochondria and a myoid region which changes in diameter during the lighting cycle indicating that rods undergo photomechanical movements. Rod nuclei are located at all levels of the outer nuclear layer and rod spherules are large and display several invaginated and superficial synaptic sites. Cone photoreceptors while large cells are smaller than the rods. They show a smaller tapering outer segment, a large distal ellipsoid of mitochondria and a prominent paraboloid of glycogen but no oil droplet within the inner segment. Judging by the width of the myoid region which remains similar throughout the lighting cycle, cones in this species show no retino-motor responses. Cone nuclei are less electron dense than rods and are also located at all levels of the outer nuclear layer. The cone synaptic pedicle is larger than that of the rods and also shows several invaginated and superficial synaptic sites.
Open Access
Maternal undernutrition model of two generations of rats: Changes in the aged retina
(Universidad de Murcia. Departamento de Biología Celular e Histología, 2023) Laurinaviciute, Guoda; Simkunaite-Rizgeliene, R.; Zalgeviciene, V.; Cepuliene, R.; Jakimaviciene, E.M.; Galgauskas, S.; Petroska, D.; Besusparis, J.; Tutkuviene, J.
The impact of maternal undernutrition on morphological changes of the retina was assessed in two generations of aged offspring. Wistar 18 rats (9 of each generation of 20-month-old female offspring; in total -27 eyes) were analyzed. The first generation offspring were born to mothers who: (a) were restricted to food only before pregnancy (pre-pregnancy); (b) whose food was restricted before and during pregnancy. The control group and all the offspring were fed normally. After enucleating the eyes, paraffin sections were stained with hematoxylin and eosin. The thickness of retina layers was measured. Cryosections were immunostained using glial fibrillary acidic protein, ionized calcium-binding adaptor molecule1, RNA-binding protein with multiple splicing for evaluation of macroglia, microglia and retinal ganglion cells by digital image analysis tools. Our data have shown atrophy of photoreceptor layer and degeneration of outer nuclear layer in all investigated groups, but less damage was found in the control group. Higher Müller cell activity and greater number of microglial cells was observed in the second generation offspring born from both restricted diet groups. Higher numbers of microglial and retinal ganglion cells were observed in the second generation in comparison to the first generation offspring. Malnutrition of the mother may be one of the possible causes of degeneration of the outer layers of the retina and activation of Müller cells in the second generation offspring. The effect of maternal nutritional restriction on the number of microglial and retinal ganglion cells is unclear
Open Access
Photoreceptor fine structure in the bobtail goanna (Tiliqua rugosa)
(Murcia : F. Hernández, 1989) Braekevelt, Charlie R.
The fine structure of the retinal photoreceptors has been studied by light and electron microscopy in the bobtail goanna (Tiliqua rugosa) an Australian diurna1 lizard. The photoreceptors in this species are readily divisible into rods or cones based on morphological criteria. Single cones are the dominate cell type with a cone:rod ratio of about 80: 1. No multiple photoreceptors were present nor was a photoreceptor mosiac observed. Cones are large cells with a short, tapering outer segment. The inner segment contains a large apical oil droplet, an ellipsoid of mitochondria and a prominent paraboloid of glycogen. Rods are slender cells with a longer ncn-tapeiing outer segment. Rod inner segnlents display an ellipsoid but no oil droplet or paraboloid. The nuclei of cones are large and vesicular while rod nuclei are smaller and displayed more heterochromatin. The synaptic pedicle of cones is larger than the spherule of rods. Both rods and cones displayed both invaginated (ribbor?) and conventional synapses with the large cones having more synaptic sites. As only light-adapted specirnens were examined it is uilcertain if either rods or cones are capable of retinomotor responses.
Open Access
Photoreceptor fine structure in the southern fiddler ray (Trygonorhina fasciata)
(Murcia : F. Hernández, 1992) Braekevelt, Charlie R.
The fine structure of the retinal lntroduction photorecéptors has been studied by light and electron microscopy in the southern fiddler ray or guitarfish (Trygonorhina fasciata). The duplex retina of this species contains only rods and single cones in a ratio of about 40:l. No multiple receptors (double cones), no repeating pattern or mosaic of photoreceptors and no retinomotor movements of these photoreceptors were noted. The rods are cylindrical cells with inner and outer segments of the same diameter. Cones are shorter, stouter cells with a conical outer segment and a wider inner segment. Rod outer segment discs display severa1 irregular incisures to give a scalloped outline to the discs while cone outer segment discs have only a single incisure. In al1 photoreceptors a non-motile cilium joins the inner and outer segments. The inner segment is the synthetic centre of photoreceptors and in this compartment is located an accumulation of mitochondria (the ellipsoid), profiles of both rough and smooth endoplasmic reticulum, prominent Golgi zones and frequent autophagic vacuoles. The nuclei of rods and cones have much the same chromatin pattern but cone nuclei are invariably located against or particularly through the externa1 limiting membrane (ELM). Numerous Landolt's clubs which are ciliated dendrites of bipolar cells as well as Müller cell processes project through the ELM, which is composed of a series of zonulae adherentes between these cells and the photoreceptors. The synaptic region of both rods (spherules) and cones (pedicles) display both invaginated (ribbon) synapses and superficial (conventional) synapses with cones showing more sites than the rods.
Open Access
Photoreceptor fine structure in the vervet monkey (Cercopithecus aethiops)
(Murcia : F. Hernández, 1987) Braekevelt, Charlie R.
The structure of the photoreceptors of the vervet monkey (Cercopithecus aethiops) has been investigated by light and electron microscopy. In this species the photoreceptors can be readily differentiated and adequately described by the classical terminology of rods and cones, with rods being the more numerous. Rods are long, slender cells while cones are shorter and stouter. Both rods and cones are highly differentiated cells and consist of an outer segment, a connecting cilium, an inner segment, a nuclear region and a synaptic process leading to a synaptic ending. Morphological differences are noted between rods and cones for the various regions of these cells.
Open Access
Quantification of Photoreceptors’ Changes in a Diabetic Retinopathy Model with Two-Photon Imaging Microscopy
(MDPI, 2024-08-11) Bautista-Elivar, N.; Avilés-Trigueros, M.; Bueno, J.M; Avilés-Trigueros, M.; Bueno, J.M.; Oftalmología, Optometría, Otorrinolaringología y Anatomía Patológica
settingsOrder Article Reprints Open AccessArticle Quantification of Photoreceptors’ Changes in a Diabetic Retinopathy Model with Two-Photon Imaging Microscopy by Nazario Bautista-Elivar 1ORCID,Marcelino Avilés-Trigueros 2ORCID andJuan M. Bueno 3,*ORCID 1 Departamento de Ingeniería Eléctrica y Electrónica, Tecnológico Nacional de México/Instituto Tecnológico de Pachuca, Pachuca 42082, Hidalgo, Mexico 2 Departamento de Oftalmología, Facultad de Medicina, Universidad de Murcia e Instituto Murciano de Investigación Biosanitaria Virgen de la Arrixaca, “Campus Mare Nostrum” de Excelencia International, 30100 Murcia, Spain 3 Laboratorio de Óptica, Instituto Universitario de Investigación en Óptica y Nanofísica, Universidad de Murcia, 30100 Murcia, Spain * Author to whom correspondence should be addressed. Int. J. Mol. Sci. 2024, 25(16), 8756; https://doi.org/10.3390/ijms25168756 Submission received: 28 June 2024 / Revised: 1 August 2024 / Accepted: 5 August 2024 / Published: 11 August 2024 (This article belongs to the Special Issue Retinal Degenerative Diseases: 2nd Edition) Downloadkeyboard_arrow_down Browse Figures Versions Notes Abstract Emerging evidence suggests that retinal neurodegeneration is an early event in the pathogenesis of diabetic retinopathy (DR), preceding the development of microvascular abnormalities. Here, we assessed the impact of neuroinflammation on the retina of diabetic-induced rats. For this aim we have used a two-photon microscope to image the photoreceptors (PRs) at different eccentricities in unstained retinas obtained from both control (N = 4) and pathological rats (N = 4). This technique provides high-resolution images where individual PRs can be identified. Within each image, every PR was located, and its transversal area was measured and used as an objective parameter of neuroinflammation. In control samples, the size of the PRs hardly changed with retinal eccentricity. On the opposite end, diabetic retinas presented larger PR transversal sections. The ratio of PRs suffering from neuroinflammation was not uniform across the retina. Moreover, the maximum anatomical resolving power (in cycles/deg) was also calculated. This presents a double-slope pattern (from the central retina towards the periphery) in both types of specimens, although the values for diabetic retinas were significantly lower across all retinal locations. The results show that chronic retinal inflammation due to diabetes leads to an increase in PR transversal size. These changes are not uniform and depend on the retinal location. Two-photon microscopy is a useful tool to accurately characterize and quantify PR inflammatory processes and retinal alterations.
Open Access
Relationship between human pupillary light reflex and circadian system status
(Public Library of Science, 2016-09-16) Bonmati-Carrión, María Ángeles; Hild, Konstanze; Isherwood, Cheryl; Sweeney, Stephen J.; Revell, Victoria L.; Skene, Debra J.; Rol, Maria Ángeles; Madrid, Juan Antonio; Anatomía Humana y Psicobiología
Intrinsically photosensitive retinal ganglion cells (ipRGCs), whose photopigment melanopsin has a peak of sensitivity in the short wavelength range of the spectrum, constitute a common light input pathway to the olivary pretectal nucleus (OPN), the pupillary light reflex (PLR) regulatory centre, and to the suprachiasmatic nuclei (SCN), the major pacemaker of the circadian system. Thus, evaluating PLR under short wavelength light (λmax 500 nm) and creating an integrated PLR parameter, as a possible tool to indirectly assess the status of the circadian system, becomes of interest. Nine monochromatic, photon-matched light stimuli (300 s), in 10 nm increments from λmax 420 to 500 nm were administered to 15 healthy young participants (8 females), analyzing: i) the PLR; ii) wrist temperature (WT) and motor activity rhythms (WA), iii) light exposure (L) pattern and iv) diurnal preference (HorneÖstberg), sleep quality (Pittsburgh) and daytime sleepiness (Epworth). Linear correlations between the different PLR parameters and circadian status index obtained from WT, WA and L recordings and scores from questionnaires were calculated. In summary, we found markers of robust circadian rhythms, namely high stability, reduced fragmentation, high amplitude, phase advance and low internal desynchronization, were correlated with a reduced PLR to 460–490 nm wavelengths. Integrated circadian (CSI) and PLR (cp-PLR) parameters are proposed, that also showed an inverse correlation. These results demonstrate, for the first time, the existence of a close relationship between the circadian system robustness and the pupillary reflex response, two non-visual functions primarily under melanopsin-ipRGC input.
Open Access
Retinal photoreceptor fine structure in the Australian Galah (Eolophus roseicapillus) (Aves)
(Murcia : F. Hernández, 1996) Braekevelt, Charlie R.; Richardson, K.C.
The retinal photoreceptors of the galah (Eolophus r-oseicapilhls), an Australian cockatoo, consist of rods, single cones and double (unequal) cones present in a ratio of about 1:3:3 respectively. The rods are long slim cells which are believed to undergo retinomotor movements. The rod inner segment displays an ellipsoid of mitochondria, much rough endoplasmic reticulum (RER), numerous polysomes and some autophagic vacuoles. No hyperboloid of glycogen was noted. Single cones show a slightly tapered outer segment, no oil droplet but a prominent ellipsoid at the apex and glycogen scattered throughout the inner segment. Double cones consist of a chief member which displays a heterogeneous oil droplet but no paraboloid of glycogen and an accessory cone with no oil droplet but a prominent paraboloid. All cones show below the ellipsoid plentiful polysomes, RER, Golgi zones and autophagic vacuoles. Cones are not felt to undergo retinomotor movements. In the light-adapted state the pigment-laden apical processes of the retinal epithelium (RPE) cells surround al1 photoreceptor types down to the inner segments. Along the length of the contiguous membranes between the two members of the double cone are membrane densifications that are presumed to be junctions. All cone photoreceptors are relatively small in diameter and hence closely packed. Rods and cones (both types) display both invaginated (ribbon) and superficial (conventional) synaptic sites.
Open Access
Retinal photoreceptor fine structure in the mallard duck (Anas platyrhinchos)
(Murcia : F. Hernández, 1990) Braekevelt, Charlie R.
The retinal photoreceptors of the mallard duck (Anas platyrhynchos) consist of rods, single cones and double (unequal) cones present in a ratio of about 1:2:1. The rods have relatively large cylindrical outer segments which in the light-adapted state reach to the retinal epithelial (RPE) cell bodies and are surrounded by the pigment-laden apical processes of these RPE cells. The inner segment displays an apically located ellipsoid of mitochondria and plentiful polysomes, some rough ER and Golgi zones. The rod nucleus is located within the outer nuclear layer and the synaptic pedicle displays both invaginated (ribbon) and superficial (conventional) synaptic sites. Single cones display a thin tapering outer segment, a large often heterogeneous oil droplet in the apical region of the inner segment, an ellipsoid of mitochondria and a prorninent paraboloid of glycogen. Double cones consist of a larger chief member which shows a thin tapering outer segment, a large heterogeneous oil droplet and a prominent paraboloid. The small accessory cone shows a thin outer segrnent, a small granular oil droplet and a paraboloid. As in the single cone, polysomes, RER and Golgi zones are also present within the inner segment. Near the outer limiting membrane the two members of the double cone show a membrane specialization on their contiguous surfaces. Both single and double cones display severa1 invaginated (ribbon) synapses as well as numerous superficial synaptic sites
Open Access
Retinal photoreceptor fine structure in the red-backed salamander (Plethodon cinereus)
(Murcia : F. Hernández, 1992) Braekevelt, Charlie R.
The retinal photoreceptors of the red-backed salamander (Plethodon cinerus) have been studied by light and electron microscopy. Rods and single cones are present in this duplex retina in a ratio of about 25: 1. The photoreceptors in this amphibian species are much larger than is reported for most vertebrates. In the light-adapted state, rods reach deep into the retinal epithelial (RPE) layer. The rod outer segment is composed of discs of uniform diameter displaying severa1 very deep incisors. The rod inner segment displays a dista1 elliposid of mitochondria and a short stout myoid region. Rod nuclei are electron dense and often protrude through the extemal limiting membrane. Rod synaptic spherules are large and display severa1 invaginated synaptic sites as well as superficial synapses. It is felt that the rods do not undergo retinomotor movements. The cone photoreceptors are much smaller than the rods and display a tapering outer segment, an unusual modified ellipsoid and a large parabolid of glycogen in the inner segment. Cone nuclei are less electron dense than rods and are located at al1 levels within the outer nuclear layer. The synaptic pedicle of the cones is larger, more electron lucent and display more synaptic sites (both invaginated and superficial) than that of rods. It is felt that cone photomechanical responses are minimal.
Open Access
Retinal photoreceptor fine structure in the short-tailed stingray. Dasyatis brevicaudata
(Murcia : F. Hernández, 1994) Braekevelt, Charlie R.
The fine structure of the retinal photoreceptors has been studied by light and electron microscopy in the short-tailed stingray (Dasyatis brevicaudata). The duplex retina of this elasmobranch contains rods and cones in a ratio of about 10:l. No multiple receptors were noted nor was a repeating or mosaic arrangenient of the cones obvious. Only lightadapted specimens were studied but retinomotor movements of the photoreceptors were felt to be minimal or absent. The rods are large cylindrical cells with inner and outer segments of much the same diameter. Cones are short stout cells with a conical outer segment and a wider inner segment. Rod outer segment discs show peripheral incisures while cones do not. The inner segment of rods and cones are rich in organelles indicating much synthetic activity. The nuclei of rods and cones appear quite similar but cone nuclei are invariably at least partially protruded through the external limiting membrane which is formed by a series of zonulae adherentes between photoreceptor cells and Miiller cells. The synaptic region of both rods and cones display both invaginated (ribbon) synapses and superficial (conventional) synapses.

Browsing by Subject "Photoreceptors"

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