39 results on '"Ekesten, Björn"'
Search Results
2. Effects of achromatic and chromatic lights on pupillary response, endocrinology, activity, and milk production in dairy cows
- Author
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Lindkvist, Sofia, Ternman, Emma, Ferneborg, Sabine, Bånkestad, Daniel, Lindqvist, Johan, Ekesten, Björn, and Agenäs, Sigrid
- Subjects
Visible Light ,Light ,genetic structures ,Physiology ,Ocular Anatomy ,Science ,Biochemistry ,Retina ,Beverages ,Animal and Dairy Science ,Ocular System ,Pregnancy ,Medicine and Health Sciences ,Animals ,Lactation ,White Light ,Particle Physics ,Lighting ,Nutrition ,Melatonin ,Photons ,Physics ,Electromagnetic Radiation ,Ecology and Environmental Sciences ,Biology and Life Sciences ,Pupil ,Hormones ,Diet ,Body Fluids ,Circadian Rhythm ,Milk ,Artificial Light ,Physical Sciences ,Daylight ,Medicine ,Cattle ,Female ,Anatomy ,Chronobiology ,Elementary Particles ,Research Article - Abstract
Artificial light can be used as a management tool to increase milk yield in dairy production. However, little is known about how cows respond to the spectral composition of light. The aim of this study was to investigate how dairy cows respond to artificial achromatic and chromatic lights. A tie-stall barn equipped with light-emitting diode (LED) light fixtures was used to create the controlled experimental light environments. Two experiments were conducted, both using dairy cows of Swedish Red and light mixtures with red, blue or white light. In experiment I, the response to light of increasing intensity on pupil size was evaluated in five pregnant non-lactating cows. In experiment II 16h of achromatic and chromatic daylight in combination with dim, achromatic night light, was tested on pregnant lactating cows during five weeks to observe long term effects on milk production, activity and circadian rhythms. Particular focus was given to possible carry over effects of blue light during the day on activity at night since this has been demonstrated in humans. Increasing intensity of white and blue light affected pupil size (P
- Published
- 2021
3. Targeted analysis of four breeds narrows equine Multiple Congenital Ocular Anomalies locus to 208 kilobases
- Author
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Andersson, Lisa S., Lyberg, Katarina, Cothran, Gus, Ramsey, David T., Juras, Rytis, Mikko, Sofia, Ekesten, Björn, Ewart, Susan, and Lindgren, Gabriella
- Published
- 2011
- Full Text
- View/download PDF
4. Deletion in the Bardet–Biedl Syndrome Gene TTC8 Results in a Syndromic Retinal Degeneration in Dogs
- Author
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Mäkeläinen, Suvi, Hellsand, Minas, van Der Heiden, Anna Darlene, Andersson, Elina, Thorsson, Elina, Hoist, Bodil S., Häggström, Jens, Ljungvall, Ingrid, Mellersh, Cathryn, Hallböök, Finn, Andersson, Göran, Ekesten, Björn, and Bergström, Tomas F.
- Subjects
congenital, hereditary, and neonatal diseases and abnormalities ,lcsh:Genetics ,primary cilia ,ciliopathy ,lcsh:QH426-470 ,retinitis pigmentosa ,Bardet–Biedl syndrome (BBS) ,Bardet-Biedl syndrome (BBS) ,genetics ,Genetik ,progressive retinal atrophy (PRA) ,BBS8 - Abstract
In golden retriever dogs, a 1 bp deletion in the canine TTC8 gene has been shown to cause progressive retinal atrophy (PRA), the canine equivalent of retinitis pigmentosa. In humans, TTC8 is also implicated in Bardet&ndash, Biedl syndrome (BBS). To investigate if the affected dogs only exhibit a non-syndromic PRA or develop a syndromic ciliopathy similar to human BBS, we recruited 10 affected dogs to the study. The progression of PRA for two of the dogs was followed for 2 years, and a rigorous clinical characterization allowed a careful comparison with primary and secondary characteristics of human BBS. In addition to PRA, the dogs showed a spectrum of clinical and morphological signs similar to primary and secondary characteristics of human BBS patients, such as obesity, renal anomalies, sperm defects, and anosmia. We used Oxford Nanopore long-read cDNA sequencing to characterize retinal full-length TTC8 transcripts in affected and non-affected dogs, the results of which suggest that three isoforms are transcribed in the retina, and the 1 bp deletion is a loss-of-function mutation, resulting in a canine form of Bardet&ndash, Biedl syndrome with heterogeneous clinical signs.
- Published
- 2020
5. Guidelines for clinical electroretinography in the dog
- Author
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Narfström, Kristina, Ekesten, Björn, Rosolen, Serge G., Spiess, Bernhard M., Percicot, Christine L., and Ofri, Ron
- Published
- 2002
- Full Text
- View/download PDF
6. Using electroretinograms to assess flicker fusion frequency in domestic hens Gallus gallus domesticus
- Author
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Lisney, Thomas J., Ekesten, Björn, Tauson, Ragnar, Håstad, Olle, and Ödeen, Anders
- Published
- 2012
- Full Text
- View/download PDF
7. A slowly progressive retinopathy in the Shetland Sheepdog
- Author
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Karlstam, Lena, Hertil, Eva, Zeiss, Caroline, Ropstad, Ernst Otto, Bjerkås, Ellen, Dubielzig, Richard R., and Ekesten, Björn
- Published
- 2011
- Full Text
- View/download PDF
8. Cone positive off-response in normal and dystrophic cats
- Author
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Ekesten, Björn and Narfström, Kristina
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- 1998
- Full Text
- View/download PDF
9. Achiasmia and unilateral optic nerve hypoplasia in an otherwise healthy infant
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Pomeranz, Howard D., Agadzi, Anthony K., and Ekesten, Björn
- Published
- 2006
10. Anterior chamber depth estimation by Scheimpflug photography
- Author
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Holmén, Jörgen B., Ekesten, Björn, and Lundgren, Björn
- Published
- 2001
11. Cone positive off-response in normal and dystrophic cats
- Author
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Ekesten, Björn and Narfström, Kristina
- Published
- 1999
12. Multiple congenital ocular anomalies in Icelandic horses
- Author
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Lindgren Gabriella, Dubielzig Richard R, Axelsson Jeanette, Andersson Lisa S, and Ekesten Björn
- Subjects
Veterinary medicine ,SF600-1100 - Abstract
Abstract Background Multiple congenital ocular anomalies (MCOA) syndrome is a hereditary congenital eye defect that was first described in Silver colored Rocky Mountain horses. The mutation causing this disease is located within a defined chromosomal interval, which also contains the gene and mutation that is associated with the Silver coat color (PMEL17, exon 11). Horses that are homozygous for the disease-causing allele have multiple defects (MCOA-phenotype), whilst the heterozygous horses predominantly have cysts of the iris, ciliary body or retina (Cyst-phenotype). It has been argued that these ocular defects are caused by a recent mutation that is restricted to horses that are related to the Rocky Mountain Horse breed. For that reason we have examined another horse breed, the Icelandic horse, which is historically quite divergent from Rocky Mountain horses. Results We examined 24 Icelandic horses and established that the MCOA syndrome is present in this breed. Four of these horses were categorised as having the MCOA-phenotype and were genotyped as being homozygous for the PMEL17 mutation. The most common clinical signs included megaloglobus, iris stromal hypoplasia, abnormal pectinate ligaments, iridociliary cysts occasionally extending into the peripheral retina and cataracts. The cysts and pectinate ligament abnormalities were observed in the temporal quadrant of the eyes. Fourteen horses were heterozygous for the PMEL17 mutation and were characterized as having the Cyst-phenotype with cysts and occasionally curvilinear streaks in the peripheral retina. Three additional horses were genotyped as PMEL17 heterozygotes, but in these horses we were unable to detect cysts or other forms of anomalies. One eye of a severely vision-impaired 18 month-old stallion, homozygous for the PMEL17 mutation was examined by light microscopy. Redundant duplication of non-pigmented ciliary body epithelium, sometimes forming cysts bulging into the posterior chamber and localized areas of atrophy in the peripheral retina were seen. Conclusions The MCOA syndrome is segregating with the PMEL17 mutation in the Icelandic Horse population. This needs to be taken into consideration in breeding decisions and highlights the fact that MCOA syndrome is present in a breed that are more ancient and not closely related to the Rocky Mountain Horse breed.
- Published
- 2011
- Full Text
- View/download PDF
13. Cone inputs to murine striate cortex
- Author
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Gouras Peter and Ekesten Björn
- Subjects
Neurosciences. Biological psychiatry. Neuropsychiatry ,RC321-571 ,Neurophysiology and neuropsychology ,QP351-495 - Abstract
Abstract Background We have recorded responses from single neurons in murine visual cortex to determine the effectiveness of the input from the two murine cone photoreceptor mechanisms and whether there is any unique selectivity for cone inputs at this higher region of the visual system that would support the possibility of colour vision in mice. Each eye was stimulated by diffuse light, either 370 (strong stimulus for the ultra-violet (UV) cone opsin) or 505 nm (exclusively stimulating the middle wavelength sensitive (M) cone opsin), obtained from light emitting diodes (LEDs) in the presence of a strong adapting light that suppressed the responses of rods. Results Single cells responded to these diffuse stimuli in all areas of striate cortex. Two types of responsive cells were encountered. One type (135/323 – 42%) had little to no spontaneous activity and responded at either the on and/or the off phase of the light stimulus with a few impulses often of relatively large amplitude. A second type (166/323 – 51%) had spontaneous activity and responded tonically to light stimuli with impulses often of small amplitude. Most of the cells responded similarly to both spectral stimuli. A few (18/323 – 6%) responded strongly or exclusively to one or the other spectral stimulus and rarely in a spectrally opponent manner. Conclusion Most cells in murine striate cortex receive excitatory inputs from both UV- and M-cones. A small fraction shows either strong selectivity for one or the other cone mechanism and occasionally cone opponent responses. Cells that could underlie chromatic contrast detection are present but extremely rare in murine striate cortex.
- Published
- 2008
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14. Baseline retinal OCT measurements in normal female beagles: The effects of eccentricity, meridian, and age on retinal layer thickness.
- Author
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Ofri, Ron and Ekesten, Björn
- Subjects
- *
OPTICAL coherence tomography , *RETROLENTAL fibroplasia , *NERVE fibers , *THICKNESS measurement , *RETINA - Abstract
Objective: Our aim was to generate baseline optical coherence tomography (OCT) measurements of retinal thickness in female Beagles and to determine how these are affected by meridian, eccentricity, and age. Methods: Twenty‐three female Beagles, including six puppies (<6 months old), six mature (1.8‐8.2 years old), and 11 elderly dogs (>11 years old) were studied. Both retinas of each dog were scanned (in 4 principal meridians) using the Heidelberg Spectralis following ophthalmic examination, refraction, and sedation. In each eye and each meridian, total retinal, outer retinal, and nerve fiber layer (NFL) thickness were measured from the disc rim up to 6 mm peripherally. Results: The canine retina is thickest dorsally and thinnest ventrally. Total retinal, outer retinal, and NFL thickness decrease progressively and significantly as a function of eccentricity. The greatest eccentricity‐dependent thinning occurs dorsally. This thinning is due mostly to NFL tapering, while the eccentricity‐dependent change in outer retinal thickness is more moderate, especially in the lateral meridian, possibly due to the presence of the visual streak. The retina is thickest in puppies, but there were no significant differences between mature and elderly dogs. Conclusions: Our results provide normative values for total, outer, and inner retinal thickness in female dogs and may facilitate OCT use in the diagnosis of canine glaucoma and inherited retinopathies. [ABSTRACT FROM AUTHOR]
- Published
- 2020
- Full Text
- View/download PDF
15. Corneal cross‐linking (CXL)—A clinical study to evaluate CXL as a treatment in comparison with medical treatment for ulcerative keratitis in horses.
- Author
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Hellander Edman, Anna, Ström, Lena, and Ekesten, Björn
- Subjects
THERAPEUTICS ,HORSES ,KERATITIS ,MICROBIAL growth ,BACTERIAL diseases ,WOUND healing - Abstract
Objective: Compare CXL treatment with medical treatment alone in horses with stromal, ulcerative keratitis. Animals studied: 24 horses (24 eyes) with stromal, ulcerative keratitis were included. Procedure: 12 horses were initially treated with CXL, and 12 horses were given conventional medical treatment. Topical medical treatment was added to horses in the CXL group if necessary. Parameters including cytology, microbial growth, time to fluorescein negativity, and time to inhibition of stromal melting were evaluated. Results: After the first day of treatments, a decrease in inflammatory signs and pain from the eye was observed in both groups. Stromal melting ceased within 24 hours regardless of treatment. CXL treatment alone was sufficient in 3 horses with noninfectious, superficial stromal ulcerations. Clinical signs of impaired wound healing were seen after 3‐14 days in corneas with suspected or proven bacterial infection treated with CXL only, most likely because of insufficient elimination of bacteria deeper in the corneal stroma or because of re‐infection from bacteria in the conjunctiva. The average decrease in stromal ulcer area per day after onset of treatment was almost identical between the groups, and no significant difference in time to fluorescein negativity was found. Conclusions: We consider CXL a possible useful adjunct treatment of corneal stromal ulcers in horses, especially for melting ulcers and as a potential alternative to prophylactic antibiotic treatment for noninfected stromal ulcers. However, CXL should not be used alone for infected or suspected infected stromal ulcers, because topical antibiotics were required in all horses with proven infectious keratitis. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
16. Age‐associated changes in the equine flash visual evoked potential.
- Author
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Ström, Lena, Michanek, Måns, and Ekesten, Björn
- Subjects
VISUAL evoked potentials ,EYE ,AGE groups ,FOALS - Abstract
Objective: To investigate age‐associated changes of flash visual evoked potentials (FVEPs) in sedated horses. Animal studied: Twenty‐eight clinically healthy Standardbred Warmblooded trotters, aged 36 hours to 28 years. Procedures: Light‐adapted FVEPs and FERGs were recorded (An‐vision RETIport, Roland‐consult, Germany) in response to flash stimuli. Sedation was obtained using alpha‐2‐agonists intravenously. Akinesia of the eyelids was induced and pupils were dilated. Results: Reproducible FVEPs and FERGs were readily recorded from all foals and horses. The FVEP waveform included up to four positive components (P1‐P5) and two negative components (N1 and N2) and FVEP waveform morphology was similar across all age groups. Some differences in peak times and amplitudes associated with increasing age were observed. FVEP amplitudes recorded from newborn foals were well above the amplitudes observed in normal adult horses and FVEP peak times were somewhat shorter. In adult horses, a significant increase in P4 peak time and a gradual decrease in amplitudes, mainly for N2P4, were seen across the life‐span. Conclusions: The overall equine FVEP waveform was similar across the normal life‐span of the horse in our cross‐sectional study. We found that the visual system of the foal seems to be well developed already at birth. Furthermore, our results showed a decrease in amplitudes and increase in some peak times with increasing age. We recommend that age‐matched controls should be used when evaluating foals and young horses in clinical practice, whereas horses over the age of three years can be compared to other adult horses. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
17. An ABCA4 loss-of-function mutation causes a canine form of Stargardt disease.
- Author
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Mäkeläinen, Suvi, Gòdia, Marta, Hellsand, Minas, Viluma, Agnese, Hahn, Daniela, Makdoumi, Karim, Zeiss, Caroline J., Mellersh, Cathryn, Ricketts, Sally L., Narfström, Kristina, Hallböök, Finn, Ekesten, Björn, Andersson, Göran, and Bergström, Tomas F.
- Subjects
STARGARDT disease ,RETINAL degeneration ,DOG diseases ,GENETIC mutation ,RHODOPSIN ,ANIMAL models in research - Abstract
Autosomal recessive retinal degenerative diseases cause visual impairment and blindness in both humans and dogs. Currently, no standard treatment is available, but pioneering gene therapy-based canine models have been instrumental for clinical trials in humans. To study a novel form of retinal degeneration in Labrador retriever dogs with clinical signs indicating cone and rod degeneration, we used whole-genome sequencing of an affected sib-pair and their unaffected parents. A frameshift insertion in the ATP binding cassette subfamily A member 4 (ABCA4) gene (c.4176insC), leading to a premature stop codon in exon 28 (p.F1393Lfs*1395), was identified. In contrast to unaffected dogs, no full-length ABCA4 protein was detected in the retina of an affected dog. The ABCA4 gene encodes a membrane transporter protein localized in the outer segments of rod and cone photoreceptors. In humans, the ABCA4 gene is associated with Stargardt disease (STGD), an autosomal recessive retinal degeneration leading to central visual impairment. A hallmark of STGD is the accumulation of lipofuscin deposits in the retinal pigment epithelium (RPE). The discovery of a canine homozygous ABCA4 loss-of-function mutation may advance the development of dog as a large animal model for human STGD. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
18. The refractive state of the eye in Icelandic horses with the Silver mutation.
- Author
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Johansson, Maria K., Fegraeus, Kim Jäderkvist, Lindgren, Gabriella, and Ekesten, Björn
- Subjects
EYE diseases ,HORSE diseases ,ANIMAL mutation ,HETEROZYGOSITY ,GENOTYPES - Abstract
Background: The syndrome Multiple Congenital Ocular Anomalies (MCOA) is a congenital eye disorder in horses. Both the MCOA syndrome and the Silver coat colour in horses are caused by the same missense mutation in the premelanosome protein (PMEL) gene. Horses homozygous for the Silver mutation (TT) are affected by multiple ocular defects causing visual impairment or blindness. Horses heterozygous for the Silver mutation (CT) have less severe clinical signs, usually cysts arising from the ciliary body iris or retina temporally. It is still unknown if the vision is impaired in horses heterozygous for the Silver mutation. A recent study reported that Comtois horses carrying the Silver mutation had significantly deeper anterior chambers of the eye compared to wild-type horses. This could potentially cause refractive errors. The purpose of the present study was to investigate if Icelandic horses with the Silver mutation have refractive errors compared to wild-type horses. One hundred and fifty-two Icelandic horses were included in the study, 71 CT horses and five TT horses. All horses were genotyped for the missense mutation in PMEL. Each CT and TT horse was matched by a wild-type (CC) horse of the same age ± 1 year. Skiascopy and a brief ophthalmic examination were performed in all horses. Association between refraction and age, eye, genotype and sex was tested by linear mixed-effect model analysis. TT horses with controls were not included in the statistical analyses as they were too few. Results: The interaction between age and genotype had a significant impact on the refractive state (P = 0.0001). CT horses older than 16 years were on average more myopic than wild-type horses of the same age. No difference in the refractive state could be observed between genotypes (CT and CC) in horses younger than 16 years. TT horses were myopic (-2 D or more) in one or both eyes regardless of age. Conclusion: Our results indicate that an elderly Icelandic horse (older than 16 years) carrying the Silver mutation is more likely to be myopic than a wild-type horse of the same age. [ABSTRACT FROM AUTHOR]
- Published
- 2017
- Full Text
- View/download PDF
19. Corneal cross-linking in 9 horses with ulcerative keratitis.
- Author
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Hellander-Edman, Anna, Makdoumi, Karim, Mortensen, Jes, and Ekesten, Björn
- Subjects
CORNEA diseases ,HORSE diseases ,CROSSLINKING (Polymerization) ,ULTRAVIOLET radiation ,VITAMIN B2 - Abstract
Background: Corneal ulcers are one of the most common eye problems in the horse and can cause varying degrees of visual impairment. Secondary infection and protease activity causing melting of the corneal stroma are always concerns in patients with corneal ulcers. Corneal collagen cross-linking (CXL), induced by illumination of the corneal stroma with ultraviolet light (UVA) after instillation of riboflavin (vitamin B2) eye drops, introduces crosslinks which stabilize melting corneas, and has been used to successfully treat infectious ulcerative keratitis in human patients. Therefore we decided to study if CXL can be performed in sedated, standing horses with ulcerative keratitis with or without stromal melting. Results: Nine horses, aged 1 month to 16 years (median 5 years) were treated with a combination of CXL and medical therapy. Two horses were diagnosed with mycotic, 5 with bacterial and 2 with aseptic ulcerative keratitis. A modified Dresden-protocol for CXL could readily be performed in all 9 horses after sedation. Stromal melting, diagnosed in 4 horses, stopped within 24 h. Eight of nine eyes became fluorescein negative in 13.5 days (median time; range 4-26 days) days after CXL. One horse developed a bacterial conjunctivitis the day after CXL, which was successfully treated with topical antibiotics. One horse with fungal ulcerative keratitis and severe uveitis was enucleated 4 days after treatment due to panophthalmitis. Conclusions: CXL can be performed in standing, sedated horses. We did not observe any deleterious effects attributed to riboflavin or UVA irradiation per se during the follow-up, neither in horses with infectious nor aseptic ulcerative keratitis. These data support that CXL can be performed in the standing horse, but further studies are required to compare CXL to conventional medical treatment in equine keratitis and to optimize the CXL protocol in this species. [ABSTRACT FROM AUTHOR]
- Published
- 2013
- Full Text
- View/download PDF
20. Inactivation of Pmel Alters Melanosome Shape But Has Only a Subtle Effect on Visible Pigmentation.
- Author
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Hellström, Anders R., Watt, Brenda, Fard, Shahrzad Shirazi, Tenza, Danièle, Mannström, Paula, Narfströ, Kristina, Ekesten, Björn, Ito, Shosuke, Wakamatsu, Kazumasa, Larsson, Jimmy, Ulfendahl, Mats, Kullander, Klas, Raposo, Graça, Kerje, Susanne, Hallböök, Finn, Marks, Michael S., and Andersson, Leif
- Subjects
BIOLOGICAL pigments ,MELANINS ,MELANOCYTES ,GENETIC mutation ,PHENOTYPES ,EPITHELIUM ,CELL culture ,LABORATORY mice - Abstract
PMEL is an amyloidogenic protein that appears to be exclusively expressed in pigment cells and forms intralumenal fibrils within early stage melanosomes upon which eumelanins deposit in later stages. PMEL is well conserved among vertebrates, and allelic variants in several species are associated with reduced levels of eumelanin in epidermal tissues. However, in most of these cases it is not clear whether the allelic variants reflect gain-of-function or loss-of-function, and no complete PMEL loss-of-function has been reported in a mammal. Here, we have created a mouse line in which the Pmel gene has been inactivated (Pmel
-/- ). These mice are fully viable, fertile, and display no obvious developmental defects. Melanosomes within Pmel-/- melanocytes are spherical in contrast to the oblong shape present in wild-type animals. This feature was documented in primary cultures of skin-derived melanocytes as well as in retinal pigment epithelium cells and in uveal melanocytes. Inactivation of Pmel has only a mild effect on the coat color phenotype in four different genetic backgrounds, with the clearest effect in mice also carrying the brown/Tyrp1 mutation. This phenotype, which is similar to that observed with the spontaneous silver mutation in mice, strongly suggests that other previously described alleles in vertebrates with more striking effects on pigmentation are dominant-negative mutations. Despite a mild effect on visible pigmentation, inactivation of Pmel led to a substantial reduction in eumelanin content in hair, which demonstrates that PMEL has a critical role for maintaining efficient epidermal pigmentation. [ABSTRACT FROM AUTHOR]- Published
- 2011
- Full Text
- View/download PDF
21. Multiple congenital ocular anomalies in Icelandic horses.
- Author
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Andersson, Lisa S., Axelsson, Jeanette, Dubielzig, Richard R., Lindgren, Gabriella, and Ekesten, Björn
- Subjects
HORSE diseases ,GENETIC mutation ,CHROMOSOMES ,PHENOTYPES ,UVEA - Abstract
Background: Multiple congenital ocular anomalies (MCOA) syndrome is a hereditary congenital eye defect that was first described in Silver colored Rocky Mountain horses. The mutation causing this disease is located within a defined chromosomal interval, which also contains the gene and mutation that is associated with the Silver coat color (PMEL17, exon 11). Horses that are homozygous for the disease-causing allele have multiple defects (MCOA-phenotype), whilst the heterozygous horses predominantly have cysts of the iris, ciliary body or retina (Cyst-phenotype). It has been argued that these ocular defects are caused by a recent mutation that is restricted to horses that are related to the Rocky Mountain Horse breed. For that reason we have examined another horse breed, the Icelandic horse, which is historically quite divergent from Rocky Mountain horses. Results: We examined 24 Icelandic horses and established that the MCOA syndrome is present in this breed. Four of these horses were categorised as having the MCOA-phenotype and were genotyped as being homozygous for the PMEL17 mutation. The most common clinical signs included megaloglobus, iris stromal hypoplasia, abnormal pectinate ligaments, iridociliary cysts occasionally extending into the peripheral retina and cataracts. The cysts and pectinate ligament abnormalities were observed in the temporal quadrant of the eyes. Fourteen horses were heterozygous for the PMEL17 mutation and were characterized as having the Cyst-phenotype with cysts and occasionally curvilinear streaks in the peripheral retina. Three additional horses were genotyped as PMEL17 heterozygotes, but in these horses we were unable to detect cysts or other forms of anomalies. One eye of a severely vision-impaired 18 month-old stallion, homozygous for the PMEL17 mutation was examined by light microscopy. Redundant duplication of non-pigmented ciliary body epithelium, sometimes forming cysts bulging into the posterior chamber and localized areas of atrophy in the peripheral retina were seen. Conclusions: The MCOA syndrome is segregating with the PMEL17 mutation in the Icelandic Horse population. This needs to be taken into consideration in breeding decisions and highlights the fact that MCOA syndrome is present in a breed that are more ancient and not closely related to the Rocky Mountain Horse breed. [ABSTRACT FROM AUTHOR]
- Published
- 2011
- Full Text
- View/download PDF
22. Retinal degeneration in nine Swedish Jämthund dogs.
- Author
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Hertil, Eva, Bergström, Tomas, Kell, Ülle, Karlstam, Lena, Ekman, Stina, and Ekesten, Björn
- Subjects
EYE diseases ,GENETIC disorders ,DOG breeds ,RETINAL degeneration ,SLIT lamp microscopy - Abstract
The Jämthund is the fourth most common breed in Sweden with approximately 1600 pups registered each year. Although it has been known that some adult dogs go blind, so they cannot hunt, the Jämthund dog has historically not been screened for hereditary eye diseases. This report describes nine Swedish Jämthund dogs with retinal degeneration. These dogs represent all Jämthund dogs diagnosed with progressive retinal atrophy (PRA) by the Swedish Eye Panel and registered with the Swedish Kennel Club from January 1998 to September 2008. The dogs were examined with indirect opthalmoscopy and slitlamp biomicroscopy. Additionally, electroretinograms (ERGs) following ECVO guidelines were performed in two dogs (one affected and one normal) and the eyes from three affected dogs were examined by light-microscopy postmortem. Typical findings were bilateral symmetric generalized retinal degeneration with tapetal hyper-reflectivity, attenuation of blood vessels and pigment clumping in the nontapetal fundus. These retinal findings progressed with time in two dogs after re-examination. Visual impairment, especially under dim light conditions, was observed in the affected dogs. ERG from one affected dog showed profoundly reduced rod responses, whereas cone responses were better preserved. Microscopic changes in the eyes from three dogs were characterized by a severe diffuse predominantly outer retinal degeneration and atrophy. Re-sequencing of the prcd-gene for eight of the nine investigated dogs revealed that none of the individuals carried disease allele that has been associated with prcd-PRA in other breeds. In conclusion, ophthalmoscopic, electroretinographic, and light-microscopic alterations observed in nine Jämthund dogs were compatible with PRA. The prcd mutation was excluded as a cause of this retinopathy. [ABSTRACT FROM AUTHOR]
- Published
- 2010
- Full Text
- View/download PDF
23. SHORT COMMUNICATION Abnormal dark-adapted ERG in cats heterozygous for a recessively inherited rod-cone degeneration.
- Author
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Ekesten, Björn and Narfström, Kristina
- Subjects
- *
EYE adaptation , *RETINAL diseases , *RETINAL degeneration , *OPHTHALMOSCOPY , *CATS , *HETEROZYGOSITY - Abstract
To study retinal function in cats homozygous and heterozygous for a recessively inherited rod-cone degeneration. Dark-adapted electroretinograms (ERGs) were performed on early affected, heterozygous (ophthalmoscopically normal), and clinically normal, nonrelated cats. Responses to blue stimuli over a 3.9-log unit range were recorded. Lower b-wave amplitudes than normal were observed in heterozygotes and early affected cats. The amplitudes of the heterozygotes took an intermediate position between normal and early affected cats. Normalized amplitude/intensity data suggest a normal dynamic range in carriers. B-wave implicit times in carriers were comparable to those of normal cats. These results show that heterozygotes have an altered retinal function, although they are ophthalmoscopically normal. It is difficult to electrophysiologically differentiate heterozygotes from affected cats with the very early stage of retinal degeneration. [ABSTRACT FROM AUTHOR]
- Published
- 2004
- Full Text
- View/download PDF
24. Co-expression of murine opsins facilitates identifying the site of cone adaptation.
- Author
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EKESTEN, BJÖRN, GOURAS, PETER, and HARGITAI, JANOS
- Published
- 2002
- Full Text
- View/download PDF
25. Pectinate ligament dysplasia and narrowing of the iridocorneal angle associated with glaucoma in the English Springer Spaniel.
- Author
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Bjerkås, Ellen, Ekesten, Björn, and Farstad, Wenche
- Subjects
- *
TONOMETRY , *GLAUCOMA - Abstract
Abstract Objective The aim of the study was to evaluate if tonometry and gonioscopy could serve as predictors of later glaucoma development in the English Springer Spaniel, a breed prone to developing primary glaucoma. Animals studied Gonioscopy was performed on 279 English Springer Spaniel dogs, 119 males and 160 females, with clinically normal eyes. In addition, 14 dogs, five males and nine females were examined for glaucoma. Results A positive relation between pectinate ligament dysplasia (PLD) and narrowing of the relative width of the ciliary cleft (RWOCC) and also between PLD, RWOCC and age was demonstrated. The prevalence of PLD was 25.5%, which is higher than in other breeds reported. A positive association was demonstrated between PLD and glaucoma, as well as between narrowing of the RWOCC and glaucoma. Glaucoma was not observed in dogs with normal appearance of the iridocorneal angle. English Springer Spaniels related to dogs with glaucoma show more narrowing of the RWOCC and more PLD than unrelated dogs. Conclusion This study demonstrates the positive association between PLD and glaucoma, between narrowing of the iridocorneal angle and glaucoma and the effect of age on the iridocorneal angle. Mating of dogs with normal iridocorneal angles appears to reduce the presence and degree of abnormal appearance of the iridocorneal angle in the offspring. However, breeding only dogs with normal iridocorneal angles without consideration of their relationship to dogs with glaucoma is not a guarantee for preventing glaucoma in the offspring. [ABSTRACT FROM AUTHOR]
- Published
- 2002
- Full Text
- View/download PDF
26. Spontaneous buphthalmos in the Djungarian hamster (Phodopus sungorus campbelli).
- Author
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Ekesten, Björn and Dubielzig, Richard
- Subjects
- *
GLAUCOMA , *HAMSTERS , *DISEASES - Abstract
Four Djungarian hamsters (Phodopus sungorus campbelli) were examined because of insidious globe enlargement, visual impairment and secondary altered behavior. Buphthalmos, deep anterior chambers, widely dilated pupils and poor to absent pupillary light reflexes were evident bilaterally in all four animals. Pale retinae and atrophic optic nerve heads were observed in the oldest hamsters. Light microscopic findings, including uveal atrophy, retinal atrophy (especially the inner retina), and a relative decrease in ganglion cells and optic nerve atrophy, were consistent with glaucoma. The etiology was unclear, but a genetic predisposition cannot be excluded. [ABSTRACT FROM AUTHOR]
- Published
- 1999
- Full Text
- View/download PDF
27. Response 'Conversion of the Kowa RC-2 camera to a digital version, instructions for use and postprocessing of the images' by Drs. Dulaurent, Bath & Isard.
- Author
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Ekesten, Björn, Stades, Frans, Allgoewer, Ingrid, and Dulaurent, Thomas
- Subjects
- *
EYE abnormalities , *DOG diseases , *IMAGE processing , *PHOTOGRAPHS , *DIGITAL cameras , *DIAGNOSIS - Published
- 2015
- Full Text
- View/download PDF
28. Equine Multiple Congenital Ocular Anomalies and Silver Coat Colour Result from the Pleiotropic Effects of Mutant PMEL.
- Author
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Andersson, Lisa S., Wilbe, Maria, Viluma, Agnese, Cothran, Gus, Ekesten, Björn, Ewart, Susan, and Lindgren, Gabriella
- Subjects
EYE abnormalities ,EYE color ,GENETIC pleiotropy ,EYE diseases ,PHYSIOLOGICAL effects of silver ,GENETIC mutation ,HORSE diseases ,GENETIC polymorphisms - Abstract
Equine Multiple Congenital Ocular Anomalies (MCOA) syndrome is a heritable eye disorder mainly affecting silver colored horses. Clinically, the disease manifests in two distinct classes depending on the horse genotype. Horses homozygous for the mutant allele present with a wide range of ocular defects, such as iris stromal hypoplasia, abnormal pectinate ligaments, megaloglobus, iridociliary cysts and cataracts. The phenotype of heterozygous horses is less severe and predominantly includes iridociliary cysts, which occasionally extend into the temporal retina. In order to determine the genetic cause of MCOA syndrome we sequenced the entire previously characterized 208 kilobase region on chromosome 6 in ten individuals; five MCOA affected horses from three different breeds, one horse with the intermediate Cyst phenotype and four unaffected controls from two different breeds. This was performed using Illumina TruSeq technology with paired-end reads. Through the systematic exclusion of all polymorphisms barring two SNPs in PMEL, a missense mutation previously reported to be associated with the silver coat colour and a non-conserved intronic SNP, we establish that this gene is responsible for MCOA syndrome. Our finding, together with recent advances that show aberrant protein function due to the coding mutation, suggests that the missense mutation is causative and has pleiotrophic effect, causing both the horse silver coat color and MCOA syndrome. [ABSTRACT FROM AUTHOR]
- Published
- 2013
- Full Text
- View/download PDF
29. Cone inputs to murine striate cortex.
- Author
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Ekesten B, Gouras P, Ekesten, Björn, and Gouras, Peter
- Abstract
Background: We have recorded responses from single neurons in murine visual cortex to determine the effectiveness of the input from the two murine cone photoreceptor mechanisms and whether there is any unique selectivity for cone inputs at this higher region of the visual system that would support the possibility of colour vision in mice. Each eye was stimulated by diffuse light, either 370 (strong stimulus for the ultra-violet (UV) cone opsin) or 505 nm (exclusively stimulating the middle wavelength sensitive (M) cone opsin), obtained from light emitting diodes (LEDs) in the presence of a strong adapting light that suppressed the responses of rods.Results: Single cells responded to these diffuse stimuli in all areas of striate cortex. Two types of responsive cells were encountered. One type (135/323-42%) had little to no spontaneous activity and responded at either the on and/or the off phase of the light stimulus with a few impulses often of relatively large amplitude. A second type (166/323-51%) had spontaneous activity and responded tonically to light stimuli with impulses often of small amplitude. Most of the cells responded similarly to both spectral stimuli. A few (18/323-6%) responded strongly or exclusively to one or the other spectral stimulus and rarely in a spectrally opponent manner.Conclusion: Most cells in murine striate cortex receive excitatory inputs from both UV- and M-cones. A small fraction shows either strong selectivity for one or the other cone mechanism and occasionally cone opponent responses. Cells that could underlie chromatic contrast detection are present but extremely rare in murine striate cortex. [ABSTRACT FROM AUTHOR]- Published
- 2008
- Full Text
- View/download PDF
30. Naphthalene-induced cataract model in rats: A comparative studybetween slit and retroillumination images, biochemical changes and naphthalenedose and duration.
- Author
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Holmén, Jörgen B., Ekesten, Björn, and Lundgren, Björn
- Subjects
- *
TREATMENT of cataracts , *NAPHTHALENE , *OPHTHALMIC photography , *THERAPEUTICS - Abstract
PURPOSE. The purpose of the study was to comparedifferent methods of photographic evaluation of cataract formation in ratsin response to different regimes of naphthalene treatment. Furthermore, weintended to study the relationship between cataract extension and biochemicalparameters. METHODS. Brown Norway rats were treated with 0.10–1.5 g naphthalene/kgbody weight, twice a week for ten weeks to induce cataract or placebo. Slitillumination and retroillumination (SI and RI) photographs were produced byan EAS-1000 instrument to document cataract formation as light-scatteringintensity. The degree of the cataractous changes was quantified in SI photographsby the peak height and the integrated peak area, and in RI photographs bythreshold setting. Finally, the lens concentration of Na[sup +] and K[sup +] and the protein composition were analyzed and correlated to the photographicanalysis. RESULTS. The degree of the cataractous changes was most linearly relatedto dose and duration when the integrated peak area was estimated. However,protein fractions were non-linearly related to the cataractous changes estimated.Alterations in concentration of Na[sup +] and K[sup +] were smallor insignificant, which indicate that naphthalene-induced cataract is notcaused by osmotic changes. The lowest possible naphthalene dose to inducecataractous changes was between 0.10 and 0.50 g/kg twice a week for ten weeks. CONCLUSIONS. 0.50 and 1.0 g naphthalene/kg twice a week appeared to beoptimal, because the rats in these groups were healthy and the cataractouschanges were consistent between animals. Thus, the combination of the animalmodel with the cataract quantification system has the potential to be usefuland reliable in studies of cataract-preventive compounds. [ABSTRACT FROM AUTHOR]
- Published
- 1999
31. In memoriam: Peter Gouras, M.D. (1930–2021).
- Author
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Allikmets, Rando, Nagasaki, Takayuki, and Ekesten, Björn
- Published
- 2021
- Full Text
- View/download PDF
32. Chapter 5 - Visual impairment
- Author
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Bjerkås, Ellen, Ekesten, Björn, Narfström, Kristina, and Grahn, Bruce
- Full Text
- View/download PDF
33. Contributors
- Author
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Bedford, Peter GC, Bjerkås, Ellen, Cook, Cynthia S, Ekesten, Björn, Grahn, Bruce H, Jones, R Gareth, Jongh, Olivier, Landis, Mary L, Monclin, Sebastien, Multari, Domenico, Narfström, Kristina, Peiffer, Robert L, Jr, Petersen-Jones, Simon M, Renwick, Peter W, Rosolen, Serge G, Stanley, Robin, Townsend, Wendy M, Wolfer, Joe, and Woods, Mike
- Full Text
- View/download PDF
34. Equine Multiple Congenital Ocular Anomalies and Silver Coat Colour Result from the Pleiotropic Effects of Mutant PMEL.
- Author
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Andersson, Lisa S., Wilbe, Maria, Viluma, Agnese, Cothran, Gus, Ekesten, Björn, Ewart, Susan, and Lindgren, Gabriella
- Subjects
- *
EYE abnormalities , *EYE color , *GENETIC pleiotropy , *EYE diseases , *PHYSIOLOGICAL effects of silver , *GENETIC mutation , *HORSE diseases , *GENETIC polymorphisms - Abstract
Equine Multiple Congenital Ocular Anomalies (MCOA) syndrome is a heritable eye disorder mainly affecting silver colored horses. Clinically, the disease manifests in two distinct classes depending on the horse genotype. Horses homozygous for the mutant allele present with a wide range of ocular defects, such as iris stromal hypoplasia, abnormal pectinate ligaments, megaloglobus, iridociliary cysts and cataracts. The phenotype of heterozygous horses is less severe and predominantly includes iridociliary cysts, which occasionally extend into the temporal retina. In order to determine the genetic cause of MCOA syndrome we sequenced the entire previously characterized 208 kilobase region on chromosome 6 in ten individuals; five MCOA affected horses from three different breeds, one horse with the intermediate Cyst phenotype and four unaffected controls from two different breeds. This was performed using Illumina TruSeq technology with paired-end reads. Through the systematic exclusion of all polymorphisms barring two SNPs in PMEL, a missense mutation previously reported to be associated with the silver coat colour and a non-conserved intronic SNP, we establish that this gene is responsible for MCOA syndrome. Our finding, together with recent advances that show aberrant protein function due to the coding mutation, suggests that the missense mutation is causative and has pleiotrophic effect, causing both the horse silver coat color and MCOA syndrome. [ABSTRACT FROM AUTHOR]
- Published
- 2013
- Full Text
- View/download PDF
35. Abnormal Appearance of the Area Centralis in Labrador Retrievers With an ABCA4 Loss-of-function Mutation.
- Author
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Ekesten B, Mäkeläinen S, Ellis S, Kjellström U, and Bergström TF
- Subjects
- ATP-Binding Cassette Transporters genetics, Animals, Dogs, Fluorescein Angiography methods, Mutation, Stargardt Disease, Vision Disorders, Visual Acuity, Macular Degeneration diagnosis, Macular Degeneration genetics
- Abstract
Purpose: To study retinal appearance and morphology in Labrador retrievers (LRs) heterozygous and homozygous for an ABCA4 loss-of-function mutation., Methods: Ophthalmic examination, including ophthalmoscopy and simple testing of vision, was performed in five ABCA4wt/wt, four ABCA4wt/InsC, and six ABCA4InsC/InsC LRs. Retinas were also examined with confocal scanning laser ophthalmoscopy (cSLO) and optical coherence tomography (OCT). Infrared and fundus autofluorescence (FAF) images were studied, and outer nuclear layer (ONL) and neuroretinal thickness were measured in the central and peripheral area centralis., Results: Clinical signs in young ABCA4InsC/InsC LRs were subtle, whereas ophthalmoscopic findings and signs of visual impairment were obvious in old ABCA4InsC/InsC LRs. Retinal appearance and vision testing was unremarkable in heterozygous LRs regardless of age. The cSLO/OCT showed abnormal morphology including ONL thinning, abnormal outer retinal layer segmentation, and focal loss of retinal pigment epithelium in the fovea equivalent in juvenile ABCA4InsC/InsC LRs. The abnormal appearance extended into the area centralis and visual streak in middle-aged ABCA4InsC/InsC and then spread more peripherally. A mild phenotype was seen on cSLO/OCT and FAF in middle-aged to old ABCA4wt/InsC LRs., Conclusions: Abnormal appearance and morphology in the fovea equivalent are present in juvenile ABCA4InsC/InsC. In the older affected LRs, the visual streak and then the peripheral retina also develop an abnormal appearance. Vision deteriorates slowly, but some vision is retained throughout life. Older heterozygotes may show a mild retinal phenotype but no obvious visual impairment. The ABCA4InsC/InsC LR is a potential model for ABCA4-mediated retinopathies/juvenile-onset Stargardt disease in a species with human-sized eyes., Translational Relevance: The ABCA4InsC mutation causes juvenile-onset abnormal appearance of the fovea equivalent in affected dogs that slowly spreads in the retina, while only a mild phenotype is seen in older carriers. This is the first non-primate, large-animal model for ABCA4-related/STGD1 retinopathies in a species with a fovea equivalent.
- Published
- 2022
- Full Text
- View/download PDF
36. Erratum to: The refractive state of the eye in Icelandic horses with the Silver mutation.
- Author
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Johansson MK, Fegraeus KJ, Lindgren G, and Ekesten B
- Published
- 2017
- Full Text
- View/download PDF
37. Equine multiple congenital ocular anomalies and silver coat colour result from the pleiotropic effects of mutant PMEL.
- Author
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Andersson LS, Wilbe M, Viluma A, Cothran G, Ekesten B, Ewart S, and Lindgren G
- Subjects
- Alleles, Animals, Chromosomes genetics, Eye Abnormalities metabolism, Genetic Association Studies methods, Genotype, Heterozygote, Homozygote, Horse Diseases metabolism, Horses metabolism, Phenotype, Polymorphism, Single Nucleotide genetics, Sequence Analysis, DNA, Eye Abnormalities genetics, Horse Diseases genetics, Horses genetics, Mutation, Missense genetics, Silver metabolism
- Abstract
Equine Multiple Congenital Ocular Anomalies (MCOA) syndrome is a heritable eye disorder mainly affecting silver colored horses. Clinically, the disease manifests in two distinct classes depending on the horse genotype. Horses homozygous for the mutant allele present with a wide range of ocular defects, such as iris stromal hypoplasia, abnormal pectinate ligaments, megaloglobus, iridociliary cysts and cataracts. The phenotype of heterozygous horses is less severe and predominantly includes iridociliary cysts, which occasionally extend into the temporal retina. In order to determine the genetic cause of MCOA syndrome we sequenced the entire previously characterized 208 kilobase region on chromosome 6 in ten individuals; five MCOA affected horses from three different breeds, one horse with the intermediate Cyst phenotype and four unaffected controls from two different breeds. This was performed using Illumina TruSeq technology with paired-end reads. Through the systematic exclusion of all polymorphisms barring two SNPs in PMEL, a missense mutation previously reported to be associated with the silver coat colour and a non-conserved intronic SNP, we establish that this gene is responsible for MCOA syndrome. Our finding, together with recent advances that show aberrant protein function due to the coding mutation, suggests that the missense mutation is causative and has pleiotrophic effect, causing both the horse silver coat color and MCOA syndrome.
- Published
- 2013
- Full Text
- View/download PDF
38. A slowly progressive retinopathy in the Shetland Sheepdog.
- Author
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Karlstam L, Hertil E, Zeiss C, Ropstad EO, Bjerkås E, Dubielzig RR, and Ekesten B
- Subjects
- Animals, Case-Control Studies, Dog Diseases pathology, Dogs, Female, Genetic Predisposition to Disease, Male, Retinal Diseases genetics, Dog Diseases genetics, Retinal Diseases veterinary
- Abstract
Objective: To describe a slowly progressive retinopathy (SPR) in Shetland Sheepdogs. Animals Forty adult Shetlands Sheepdogs with ophthalmoscopic signs of SPR and six normal Shetland Sheepdogs were included in the study., Procedure: Ophthalmic examination including slit-lamp biomicroscopy and ophthalmoscopy was performed in all dogs. Electroretinograms and obstacle course-test were performed in 13 affected and 6 normal dogs. The SPR dogs were subdivided into two groups according to their dark-adapted b-wave amplitudes. SPR1-dogs had ophthalmoscopic signs of SPR, but normal dark-adapted b-wave amplitudes. Dogs with both ophthalmoscopic signs and subnormal, dark-adapted b-wave amplitudes were assigned to group SPR2. Eyes from two SPR2 dogs were obtained for microscopic examination., Results: The ophthalmoscopic changes included bilateral, symmetrical, greyish discoloration in the peripheral tapetal fundus with normal or marginally attenuated vessels. Repeated examination showed that the ophthalmoscopic changes slowly spread across the central parts of the tapetal fundus, but did not progress to obvious neuroretinal thinning presenting as tapetal hyper-reflectivity. The dogs did not appear seriously visually impaired. SPR2 showed significantly reduced b-wave amplitudes throughout dark-adaptation. Microscopy showed thinning of the outer nuclear layer and abnormal appearance of rod and cone outer segments. Testing for the progressive rod-cone degeneration ( prcd )-mutation in three dogs with SPR was negative., Conclusion: Slowly progressive retinopathy is a generalized rod-cone degeneration that on ophthalmoscopy looks similar to early stages of progressive retinal atrophy. The ophthalmoscopic findings are slowly progressive without tapetal hyper-reflectivity. Visual impairment is not obvious and the electroretinogram is more subtly altered than in progressive retinal atrophy. The etiology remains unclear. SPR is not caused by the prcd-mutation., (© 2011 American College of Veterinary Ophthalmologists.)
- Published
- 2011
- Full Text
- View/download PDF
39. Abnormal dark-adapted ERG in cats heterozygous for a recessively inherited rod-cone degeneration.
- Author
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Ekesten B and Narfström K
- Subjects
- Animals, Case-Control Studies, Cats, Electroretinography veterinary, Female, Genetic Predisposition to Disease, Male, Pedigree, Retinal Degeneration genetics, Retinal Degeneration physiopathology, Cat Diseases genetics, Cat Diseases physiopathology, Dark Adaptation physiology, Photoreceptor Cells physiopathology, Retinal Degeneration veterinary
- Abstract
Purpose: To study retinal function in cats homozygous and heterozygous for a recessively inherited rod-cone degeneration., Methods: Dark-adapted electroretinograms (ERGs) were performed on early affected, heterozygous (ophthalmoscopically normal), and clinically normal, nonrelated cats. Responses to blue stimuli over a 3.9-log unit range were recorded., Results: Lower b-wave amplitudes than normal were observed in heterozygotes and early affected cats. The amplitudes of the heterozygotes took an intermediate position between normal and early affected cats. Normalized amplitude/intensity data suggest a normal dynamic range in carriers. B-wave implicit times in carriers were comparable to those of normal cats., Conclusions: These results show that heterozygotes have an altered retinal function, although they are ophthalmoscopically normal. It is difficult to electrophysiologically differentiate heterozygotes from affected cats with the very early stage of retinal degeneration.
- Published
- 2004
- Full Text
- View/download PDF
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