Canine S- and M/L- cone electroretinograms
Full-field flash electroretinography is an electrodiagnostic method used to examine the function of retinal cells. Light stimulation of the eye elicits electrical potentials in the retina. By aid of a corneal electrode and a reference electrode close to the back of the eye, the electrical potentials...
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| Formato: | Second cycle, A2E |
| Lenguaje: | sueco Inglés |
| Publicado: |
2014
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| Acceso en línea: | https://stud.epsilon.slu.se/6533/ |
| _version_ | 1855571027605585920 |
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| author | Rydhed, Erica |
| author_browse | Rydhed, Erica |
| author_facet | Rydhed, Erica |
| author_sort | Rydhed, Erica |
| collection | Epsilon Archive for Student Projects |
| description | Full-field flash electroretinography is an electrodiagnostic method used to examine the function of retinal cells. Light stimulation of the eye elicits electrical potentials in the retina. By aid of a corneal electrode and a reference electrode close to the back of the eye, the electrical potentials can be recorded and presented as an electroretinogram (ERG). ERGs driven by mainly one type of cones can be used to examine the function of a single cone class. In human beings, studies have shown the cone class sensitive to light of short wavelengths, the S-cones, to be more vulnerable to acquired damage than the other cone classes (Daley et al., 1987; Gouras et al., 1993; Greenstein et al., 1989).
Dogs have two cone classes, S-cones, and M/L-cones (most sensitive to medium to long wavelengths). Hitherto, no guidelines or protocols for separating S- and M/L-cone driven ERGs in the dog have been published. Hence we know little about how each of these two cone classes are affected in different canine retinal diseases and there may be diseases still unrevealed due to the lack of proper diagnostics. The aim of this study was to separate and examine S- and M/L- cone driven canine ERGs.
In this study, S- and M/L-cone driven ERGs were recorded using chromatic stimuli and selective chromatic adaptation in six healthy Beagle dogs. The method means that a light stimulus with a wavelength that maximally stimulates one cone class is presented on a bright chromatic background that saturates the rods and strongly supresses the responses from the cone type/types that are not of interest. We used a violet light stimulus (411 nm) on a steady, bright, red background light (627 nm) to elicit responses mainly driven by the canine S-cones. To examine the pure M/L-cone driven ERG, the violet light was instead used as background light whilst the red light was used as the stimulus. In addition, a second experiment was performed where we used the two stimuli on a steady, bright, blue background (470 nm) that would suppress the S- and M/L-cones almost equally, as well as bleach the rhodopsin completely.
Selective chromatic adaptation provided non-univariant responses despite the use of equal relative light intensities for the stimuli, which suggests that we were stimulating two different cone mechanisms. The S-cone driven ERG had longer b-wave implicit times and lower b-wave amplitudes, which seemed to saturate at lower stimulus intensities compared to the M/L-cone driven ERG, which had shorter b-wave implicit times and higher b-wave amplitudes that increased over a larger range of stimulus intensities. A prominent d-wave (response to the cessation of light) was seen on the M/L-cone driven ERG, whilst this was absent, or at least not obvious, on the S-cone driven ERG. Our results are in agreement with the results from a study of feline cone ERGs (Zrenner & Gouras, 1979). |
| format | Second cycle, A2E |
| id | RepoSLU6533 |
| institution | Swedish University of Agricultural Sciences |
| language | Swedish Inglés |
| publishDate | 2014 |
| publishDateSort | 2014 |
| record_format | eprints |
| spelling | RepoSLU65332014-03-21T15:52:03Z https://stud.epsilon.slu.se/6533/ Canine S- and M/L- cone electroretinograms Rydhed, Erica Veterinary science and hygiene - General aspects Animal diseases Technology Full-field flash electroretinography is an electrodiagnostic method used to examine the function of retinal cells. Light stimulation of the eye elicits electrical potentials in the retina. By aid of a corneal electrode and a reference electrode close to the back of the eye, the electrical potentials can be recorded and presented as an electroretinogram (ERG). ERGs driven by mainly one type of cones can be used to examine the function of a single cone class. In human beings, studies have shown the cone class sensitive to light of short wavelengths, the S-cones, to be more vulnerable to acquired damage than the other cone classes (Daley et al., 1987; Gouras et al., 1993; Greenstein et al., 1989). Dogs have two cone classes, S-cones, and M/L-cones (most sensitive to medium to long wavelengths). Hitherto, no guidelines or protocols for separating S- and M/L-cone driven ERGs in the dog have been published. Hence we know little about how each of these two cone classes are affected in different canine retinal diseases and there may be diseases still unrevealed due to the lack of proper diagnostics. The aim of this study was to separate and examine S- and M/L- cone driven canine ERGs. In this study, S- and M/L-cone driven ERGs were recorded using chromatic stimuli and selective chromatic adaptation in six healthy Beagle dogs. The method means that a light stimulus with a wavelength that maximally stimulates one cone class is presented on a bright chromatic background that saturates the rods and strongly supresses the responses from the cone type/types that are not of interest. We used a violet light stimulus (411 nm) on a steady, bright, red background light (627 nm) to elicit responses mainly driven by the canine S-cones. To examine the pure M/L-cone driven ERG, the violet light was instead used as background light whilst the red light was used as the stimulus. In addition, a second experiment was performed where we used the two stimuli on a steady, bright, blue background (470 nm) that would suppress the S- and M/L-cones almost equally, as well as bleach the rhodopsin completely. Selective chromatic adaptation provided non-univariant responses despite the use of equal relative light intensities for the stimuli, which suggests that we were stimulating two different cone mechanisms. The S-cone driven ERG had longer b-wave implicit times and lower b-wave amplitudes, which seemed to saturate at lower stimulus intensities compared to the M/L-cone driven ERG, which had shorter b-wave implicit times and higher b-wave amplitudes that increased over a larger range of stimulus intensities. A prominent d-wave (response to the cessation of light) was seen on the M/L-cone driven ERG, whilst this was absent, or at least not obvious, on the S-cone driven ERG. Our results are in agreement with the results from a study of feline cone ERGs (Zrenner & Gouras, 1979). Elektroretinografi är en elektrodiagnostisk metod som används för att undersöka funktionen hos celler i retina. Metoden bygger på att ljusstimulering av ögat ger upphov till elektriska potentialer över retina. Registrering av dessa signaler sker via en corneaelektrod samt en referenselektrod nära ögats laterala kant och presenteras i form av ett elektroretinogram (ERG). Selektiva ERG huvudsakligen drivna av en viss typ av tappar kan användas för att undersöka funktionen hos en viss tapp-klass i taget. Studier på människa har visat att S-tapparna, tapp-klassen känsliga för ljus av korta våglängder, är mer sårbara än människans två andra tappar, både vid flertalet primära ögonsjukdomar och vid sekundär påverkan på näthinnan vid systemiska sjukdomar (Daley et al., 1987; Gouras et al., 1993; Greenstein et al., 1989). Hunden har två typer av tappar, S-tappar, samt M/L-tappar, de senare är mest känsliga för ljus av mellanlånga till långa våglängder. Hittills har inga riktlinjer eller protokoll som gör det möjligt att separera hundens S- och M/L-tapp-drivna ERG publicerats. Således är det idag okänt hur S- respektive M/L-tapparna hos hund påverkas vid olika patologiska processer i retina och det kan finnas sjukdomar som ännu inte upptäckts på grund av avsaknad av metoder för att kunna diagnosticera dem. Syftet med denna studie var att separera och undersöka S- och M/L-tappsdrivna ERG hos hund. I studien registrerades S- och M/L-drivna ERG med hjälp av kromatiska stimuli och selektiv kromatisk adaptation hos sex friska beagle-hundar. Detta innebär att ett ljusstimulus av en våglängd som maximalt stimulerar en viss tapp-klass presenteras på ett starkt bakgrundsljus som både mättar stavar och optimalt trycker ner responsen från tapp-klasserna som inte är av intresse. Vi använde ett violett ljus (411 nm) på ett starkt, rött bakgrundsljus (627 nm) för att erhålla ett huvudsakligen S-tappsdrivet ERG. För att erhålla ett M/L-tappsdrivet ERG användes istället det röda ljuset som stimulus och det violetta ljuset som bakgrundsljus. Dessutom presenterades dessa två stimuli, samt ett blått (470 nm) stimulus, på en stark blå (470 nm) bakgrund som hämmade S- och M/L-tapparna ungefär lika mycket, samt mättade stavarna fullständigt. Selektiv kromatisk adaptation gav upphov till ERG-kurvor med skilda utseenden, trots likvärdiga stimulusljusintensiteter, vilket indikerar att vi stimulerade två olika cellmekanismer. Den S-tapp-drivna kurvan hade en längre b-vågsimplicittider samt lägre b-vågsamplituder, vilka tycktes mättas vid lägre ljusintensiteter jämfört med den M/L-tappsdrivna kurvan, som följaktligen hade kortare b-vågsimplicittider och högre b-vågsamplituder. Medan en tydlig d-våg (en respons på då ljuset släckts) sågs när M/L-tapparna stimulerades, kunde en sådan inte urskiljas på S-tappsdrivna ERGn. Resultaten överensstämmer väl med en tidigare studie av S-tapps-drivet ERG på katt (Zrenner & Gouras, 1979). 2014-03-20 Second cycle, A2E NonPeerReviewed application/pdf sv https://stud.epsilon.slu.se/6533/7/rydhed_e_140320.pdf Rydhed, Erica, 2014. Canine S- and M/L- cone electroretinograms. Second cycle, A2E. Uppsala: (VH) > Dept. of Clinical Sciences (until 231231) <https://stud.epsilon.slu.se/view/divisions/OID-715.html> urn:nbn:se:slu:epsilon-s-3138 eng |
| spellingShingle | Veterinary science and hygiene - General aspects Animal diseases Technology Rydhed, Erica Canine S- and M/L- cone electroretinograms |
| title | Canine S- and M/L- cone electroretinograms |
| title_full | Canine S- and M/L- cone electroretinograms |
| title_fullStr | Canine S- and M/L- cone electroretinograms |
| title_full_unstemmed | Canine S- and M/L- cone electroretinograms |
| title_short | Canine S- and M/L- cone electroretinograms |
| title_sort | canine s- and m/l- cone electroretinograms |
| topic | Veterinary science and hygiene - General aspects Animal diseases Technology |
| url | https://stud.epsilon.slu.se/6533/ https://stud.epsilon.slu.se/6533/ |