The Experts below are selected from a list of 255 Experts worldwide ranked by ideXlab platform
Kristina Narfström - One of the best experts on this subject based on the ideXlab platform.
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A high-resolution 15,000Rad radiation hybrid panel for the domestic Cat
Cytogenetic and Genome Research, 2012Co-Authors: Leslie H. Bach, Kristina Narfström, Barbara Gandolfi, Jennifer C. Grahn, L. V. Millon, Michael S. Kent, Shelley A. Cole, James C. Mullikin, Robert A. Grahn, Leslie A. LyonsAbstract:The current genetic and recombination maps of the Cat have fewer than 3,000 markers and a resolution limit greater than 1 Mb. To complement the first-generation domestic Cat maps, support higher resolution mapping studies, and aid genome assembly in specific areas as well as in the whole genome, a 15,000Rad radiation hybrid (RH) panel for the domestic Cat was generated. Fibroblasts from the female Abyssinian Cat that was used to generate the Cat genomic sequence were fused to a Chinese hamster cell line (A23), producing 150 hybrid lines. The clones were initially characterized using 39 short tandem repeats (STRs) and 1,536 SNP markers. The utility of whole-genome amplifiCation in preserving and extending RH panel DNA was also tested using 10 STR markers; no significant difference in retention was observed. The resolution of the 15,000Rad RH panel was established by constructing framework maps across 10 different 1-Mb regions on different feline chromosomes. In these regions, 2-point analysis was used to estimate RH distances, which compared favorably with the estimation of physical distances. The study demonstrates that the 15,000Rad RH panel constitutes a powerful tool for constructing high-resolution maps, having an average resolution of 40.1 kb per marker across the ten 1-Mb regions. In addition, the RH panel will complement existing genomic resources for the domestic Cat, aid in the accurate re-assemblies of the forthcoming Cat genomic sequence, and support cross-species genomic comparisons.
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Retinal degeneration in the Abyssinian and Somali Cat (rdAc): correlation between genotype and phenotype and rdAc allele frequency in two continents
Veterinary Ophthalmology, 2009Co-Authors: Kristina Narfström, Stephen J. O'brien, Victor A. David, Oswald Jarret, Julia A. Beatty, Vanessa R. Barrs, David A. Wilkie, Marilyn Menotti-raymondAbstract:Objective To characterize hereditary retinal degeneration in the Abyssinian Cat (rdAc) in a recently established closed colony segregating for the rdAc mutation, and evaluate possible differences in the age of onset and progression of disease phenotype since the initial description of rdAc 25 years ago. The sample size of an earlier study was increased in order to determine the allele frequency in Abyssinian and Somali Cats on a worldwide basis. Animals studied Twenty rdAc affected Cats from the closed animal facility, 87 Abyssinian and Somali Cats for study of genotype–phenotype concordance, and DNA from 131 Abyssinian and Somali Cats from Scandinavia, the UK and Australia for evaluation of the rdAc allele frequency. Procedures DNA was extracted from blood and buccal swabs using commercially available kits, followed by genotyping. Ophthalmic examinations were performed in the USA and Sweden by two board-certified veterinary ophthalmologists. Results A greater variation in the age of onset and progression of the disease was observed compared to that previously described. An excellent correlation between genotype and phenotype was observed. A population genetic survey revealed that the rdAc allele is in moderate abundance in the Abyssinian breed in Europe and Australia. Surprisingly, homozygosity for the mutant allele was observed in a Siamese Cat with ophthalmoscopic findings similar to those originally described for affected rdAc individuals. Conclusions Alertness to the potential of rdAc is needed on the part of the veterinary ophthalmology community, not only in Abyssinian and Somali Cats but possibly also in other related Cat breeds.
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Functional and structural assessment of retinal sheet allograft transplantation in feline hereditary retinal degeneration.
Veterinary Ophthalmology, 2009Co-Authors: Magdalene J. Seiler, Ragnheidur Bragadottir, Robert B. Aramant, Mathias W. Seeliger, Melissa J. Mahoney, Kristina NarfströmAbstract:Purpose To investigate whether sheets of fetal retinal allografts can integrate into the dystrophic Abyssinian Cat retina with progressive rod cone degeneration. Methods Fetal retinal sheets (Cat gestational day 42), incubated with BDNF microspheres, were transplanted to the subretinal space of four Cats at an early disease stage. Cats were studied by fundus examinations, bilateral full-field flash ERGs, and indocyanine green and fluorescein angiograms up to 4 months following surgery. E42 donor and transplanted eyes were analyzed by histology and immunohistochemistry for retinal markers. Results Funduscopy and angiography showed good integration of the transplants in two of four Cats, including extension of host blood vessels into the transplant and some scarring in the host. In these two, transplants were found in the subretinal space with laminated areas, with photoreceptor outer segments in normal contacts with the host retinal pigment epithelium. In some areas, transplants appeared to be well-integrated within the host neural retina. Neither of these two Cats showed functional improvement in ERGs. In the other two Cats, only remnants of donor tissue were left. Transplants stained for all investigated cellular markers. No PKC immunoreactivity was detected in the fetal donor retina at E42, but developed in the 4-month-old grafts. Conclusions Fetal sheet transplants can integrate well within a degenerating Cat retina and develop good lamination of photoreceptors. Functional improvement was not demonstrated by ERG in Cats with well-laminated grafts. Transplants need to be further evaluated in Cat host retinas with a more advanced retinal degeneration using longer follow-up times.
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Choroidal microcirculation in Abyssinian Cats with hereditary rod–cone degeneration
Experimental Eye Research, 2008Co-Authors: Christian-albrecht May, Kristina NarfströmAbstract:Blood flow in the choroid of eyes with retinal degeneration is normally reduced. In the Abyssinian Cat, where no changes in choroidal blood flow were observed recently, a closer morphological analysis revealed that two factors might have lead to this finding. (a) The Cat's eye consists of a tapetum lucidum where 15.5 μm microspheres cannot reach the precapillary branching in contrast to the non-tapetal areas, where microspheres were loCated right next to the choriocapillaris. This fact has not yet been described and might be important for further physiological measurements in eyes of species with a tapetum lucidum. (b) The tapetal cells themselves might have a protective role for the choriocapillaris and RPE during retinal degeneration in this specific animal model. Even in late stages of retinal degeneration the RPE and choriocapillaris in areas covered by the tapetum lucidum were not affected whereas non-tapetal areas showed loss of RPE and capillaries.
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neural precursors isolated from the developing Cat brain show retinal integration following transplantation to the retina of the dystrophic Cat
Veterinary Ophthalmology, 2007Co-Authors: Henry Klassen, Philip H Schwartz, Boback Ziaeian, Hubert E Nethercott, Michael J Young, Ragnheidur Bragadottir, Gregory E Tullis, Karin Warfvinge, Kristina NarfströmAbstract:The Cat has served as an important nonrodent research model for neurophysiology and retinal degenerative disease processes, yet very little is known about feline neural precursor cells. To culture these cells and evaluate marker expression, brains were dissected from 45-day-old fetuses, enzymatically dissociated, and grown in the presence of EGF, bFGF and PDGF. Expanded cells widely expressed nestin, Sox2, Ki-67, fusin (CXCR4) and vimentin, while subpopulations expressed A2B5, GFAP, or β -III tubulin. Precursors prelabeled with BrdU and/or transduced with a recombinant lentivirus that expresses GFP were transplanted subretinally in five dystrophic Abyssinian Cats. Two to 4 weeks following surgery, histology showed survival of grafted cells in three of the animals. Labeled cells were found in the neuroretina and RPE layer, as well as in the vitreous and the vicinity of Bruch’s membrane. There was no evidence of an immunologic response in any of the eyes. Neural precursor cells can therefore be cultured from the developing Cat brain and survive as allografts for up to 4 weeks without immune suppression. The feasibility of deriving and transplanting feline neural precursor cells, combined with the availability of the dystrophic Abyssinian Cat, provide a new feline model system for the study of retinal repair.
Barbara Wiggert - One of the best experts on this subject based on the ideXlab platform.
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An early decrease in interphotoreceptor retinoid-binding protein gene expression in Abyssinian Cats homozygous for hereditary rod-cone degeneration
Cell and Tissue Research, 1994Co-Authors: Barbara Wiggert, Theo Veen, Geetha Kutty, Ling Lee, John Nickerson, Sven Erik G. Nilsson, Gerald J. Chader, Kristina NarfströmAbstract:Levels of interphotoreceptor retinoid-binding protein (IRBP) protein and message in retinas of Abyssinian Cats homozygous for progressive rod-cone degeneration were determined at early ages, well before the onset of clinical retinal degeneration. IRBP gene expression was assessed by immunochemical quantitation of IRBP protein, and by Northern blotting and slot-blotting of total RNA using a human IRBP cDNA probe. Morphology was assessed by electron microscopy and immunocytochemistry. Levels of both IRBP protein and message in affected Abyssinian Cat retinas were significantly reduced below normal as early as 4 weeks of age at the earliest stage of retinal disorientation. Opsin mRNA was more abundant in affected Abyssininian Cat retinas than in control retinas. This was at least 1 year before the onset of clinical symptoms. The reduction in IRBP gene expression to levels significantly below normal well before the onset of retinal degeneration in affected Abyssinian Cat retinas indiCates that this represents a primary defect or at least an early problem that could itself cause adverse effects.
Sven Erik G. Nilsson - One of the best experts on this subject based on the ideXlab platform.
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An early decrease in interphotoreceptor retinoid-binding protein gene expression in Abyssinian Cats homozygous for hereditary rod-cone degeneration
Cell and Tissue Research, 1994Co-Authors: Barbara Wiggert, Theo Veen, Geetha Kutty, Ling Lee, John Nickerson, Sven Erik G. Nilsson, Gerald J. Chader, Kristina NarfströmAbstract:Levels of interphotoreceptor retinoid-binding protein (IRBP) protein and message in retinas of Abyssinian Cats homozygous for progressive rod-cone degeneration were determined at early ages, well before the onset of clinical retinal degeneration. IRBP gene expression was assessed by immunochemical quantitation of IRBP protein, and by Northern blotting and slot-blotting of total RNA using a human IRBP cDNA probe. Morphology was assessed by electron microscopy and immunocytochemistry. Levels of both IRBP protein and message in affected Abyssinian Cat retinas were significantly reduced below normal as early as 4 weeks of age at the earliest stage of retinal disorientation. Opsin mRNA was more abundant in affected Abyssininian Cat retinas than in control retinas. This was at least 1 year before the onset of clinical symptoms. The reduction in IRBP gene expression to levels significantly below normal well before the onset of retinal degeneration in affected Abyssinian Cat retinas indiCates that this represents a primary defect or at least an early problem that could itself cause adverse effects.
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Photoreceptor degeneration and loss of immunoreactive GABA in the Abyssinian Cat retina.
Experimental Eye Research, 1991Co-Authors: Berndt Ehinger, Kristina Narfström, Sven Erik G. Nilsson, T. Van VeenAbstract:Abstract GABA (gamma-amino butyric acid) and its synthesizing enzyme, GAD (glutamate decarboxylase; EC 4. 1. 1. 15) were localized in the retina of Abyssinian Cats homozygous for a recessively inherited retinal degenerative disorder which in several respects is similar to the human disease, retinitis pigmentosa. Clinically normal mongrel Cats and heterozygous Abyssinian Cats were studied for comparison. The GABA and GAD immunoreactive neurons of the heterozygous or young homozygous (clinically unaffected animals) had the same distribution and morphology as normal mongrel European type Cats. The neuronal GABA Immunoreactivity in both the inner and outer parts of the retina gradually disappeared in the course of the disease, with little or no loss of GAD immunoreactive neurons. Early in the disease, the changes were most severe in patches in the mid periphery of the eye and then spread both centrally and peripherally. Loss of photoreceptors was a prerequisite for the loss of GABA immunoreactivity. The observations show that retinal changes are not limited to the photoreceptors. The GABA loss is not likely to be due to a loss of neurons, because of the persistence of GAD immunoreactive neurons.
John Nickerson - One of the best experts on this subject based on the ideXlab platform.
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An early decrease in interphotoreceptor retinoid-binding protein gene expression in Abyssinian Cats homozygous for hereditary rod-cone degeneration
Cell and Tissue Research, 1994Co-Authors: Barbara Wiggert, Theo Veen, Geetha Kutty, Ling Lee, John Nickerson, Sven Erik G. Nilsson, Gerald J. Chader, Kristina NarfströmAbstract:Levels of interphotoreceptor retinoid-binding protein (IRBP) protein and message in retinas of Abyssinian Cats homozygous for progressive rod-cone degeneration were determined at early ages, well before the onset of clinical retinal degeneration. IRBP gene expression was assessed by immunochemical quantitation of IRBP protein, and by Northern blotting and slot-blotting of total RNA using a human IRBP cDNA probe. Morphology was assessed by electron microscopy and immunocytochemistry. Levels of both IRBP protein and message in affected Abyssinian Cat retinas were significantly reduced below normal as early as 4 weeks of age at the earliest stage of retinal disorientation. Opsin mRNA was more abundant in affected Abyssininian Cat retinas than in control retinas. This was at least 1 year before the onset of clinical symptoms. The reduction in IRBP gene expression to levels significantly below normal well before the onset of retinal degeneration in affected Abyssinian Cat retinas indiCates that this represents a primary defect or at least an early problem that could itself cause adverse effects.
Ling Lee - One of the best experts on this subject based on the ideXlab platform.
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An early decrease in interphotoreceptor retinoid-binding protein gene expression in Abyssinian Cats homozygous for hereditary rod-cone degeneration
Cell and Tissue Research, 1994Co-Authors: Barbara Wiggert, Theo Veen, Geetha Kutty, Ling Lee, John Nickerson, Sven Erik G. Nilsson, Gerald J. Chader, Kristina NarfströmAbstract:Levels of interphotoreceptor retinoid-binding protein (IRBP) protein and message in retinas of Abyssinian Cats homozygous for progressive rod-cone degeneration were determined at early ages, well before the onset of clinical retinal degeneration. IRBP gene expression was assessed by immunochemical quantitation of IRBP protein, and by Northern blotting and slot-blotting of total RNA using a human IRBP cDNA probe. Morphology was assessed by electron microscopy and immunocytochemistry. Levels of both IRBP protein and message in affected Abyssinian Cat retinas were significantly reduced below normal as early as 4 weeks of age at the earliest stage of retinal disorientation. Opsin mRNA was more abundant in affected Abyssininian Cat retinas than in control retinas. This was at least 1 year before the onset of clinical symptoms. The reduction in IRBP gene expression to levels significantly below normal well before the onset of retinal degeneration in affected Abyssinian Cat retinas indiCates that this represents a primary defect or at least an early problem that could itself cause adverse effects.
