Working Men's Co-operative Organizations in Great Britain

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Genetic and Phenotypic Variations of Inherited Retinal Diseases in Dogs: The Power of Within- and Across-Breed Studies

Considerable clinical and molecular variations have been known in retinal blinding diseases in man and also in dogs. Different forms of retinal diseases occur in specific breed(s) caused by mutations segregating within each isolated breeding population. While molecular studies to find genes and mutations underlying retinal diseases in dogs have benefited largely from the phenotypic and genetic uniformity within a breed, within- and across-breed variations have often played a key role in elucidating the molecular basis. The increasing knowledge of phenotypic, allelic, and genetic heterogeneities in canine retinal degeneration has shown that the overall picture is rather more complicated than initially thought. Over the past 20 years, various approaches have been developed and tested to search for genes and mutations underlying genetic traits in dogs, depending on the availability of genetic tools and sample resources. Candidate gene, linkage analysis, and genome-wide association studies have so far identified 24 mutations in 18 genes underlying retinal diseases in at least 58 dog breeds. Many of these genes have been associated with retinal diseases in humans, thus providing opportunities to study the role in pathogenesis and in normal vision. Application in therapeutic interventions such as gene therapy has proven successful initially in a naturally occurring dog model followed by trials in human patients. Other genes whose human homologs have not been associated with retinal diseases are potential candidates to explain equivalent human diseases and contribute to the understanding of their function in vision

Age-Dependent Disease Expression Determines Remodeling of the Retinal Mosaic in Carriers of \u3cem\u3eRPGR\u3c/em\u3e Exon ORFn\u3csub\u3e15\u3c/sub\u3e Mutations

PURPOSE. To characterize the retinal histopathology in carriers of X-linked progressive retinal atrophy (XLPRA1 and XLPRA2), two canine models of X-linked retinitis pigmentosa caused, respectively, by a stop and a frameshift mutation in RPGRORF15. METHODS. Retinas of XLPRA2 and XLPRA1 carriers of different ages were processed for morphologic evaluation, TUNEL assay, and immunohistochemistry. Cell-specific markers were used to examine retinal remodeling events. RESULTS. A mosaic pattern composed of patches of diseased and normal retina was first detected in XLPRA2 carriers at 4.9 weeks of age. A peak of photoreceptor cell death led to focal rod loss; however, in these patches an increased density of cones was found to persist over time. Patches of disease gradually disappeared so that by 39 weeks of age the overall retinal morphology, albeit thinner, had improved lamination. In older XLPRA2 carriers (≥8.8 years), extended regions of severe degeneration occurred in the peripheral/mid-peripheral retina. In XLPRA1 carriers, opsin mislocalization and rare events of rod death were detected by TUNEL assay at 20 weeks of age; however, only patchy degeneration was seen by 1.4 years and was still apparent at 7.8 years. CONCLUSIONS. The time of onset and the progression of the disease differed between the two models. In the early-onset form (XLPRA2) the morphologic appearance of the retinal mosaic changed as a function of age, suggesting that structural plasticity persists in the early postnatal canine retina as mutant photoreceptors die. In the late-onset form (XLPRA1), patches of disease persisted until later ages

Operating in the Dark: A Night-Vision System for Surgery in Retinas Susceptible to Light Damage

A standard operating microscope was modified with a bandpass infrared filter in the light path and infrared image intensifiers for each of the 2 eyepieces. We evaluated this system for subretinal injections in normal control dogs and those with a mutation in the rhodopsin gene. Rhodopsin-mutant dogs are a model for human autosomal dominant retinitis pigmentosa, and their retinas degenerate faster when exposed to modest light levels as used in routine clinical examinations. We showed that the mutant retinas developed severe generalized degeneration when exposed to the standard operating microscope light but not the infrared light. The modified operating microscope provided an excellent view of the ocular fundus under infrared illumination and allowed us to perform subretinal injections in the retinas of the rhodopsin-mutant dogs without any subsequent light-induced retinal degeneration. The first description of light-induced retinal damage showed that exposure of albino rats to visible light intensities ordinarily encountered in the laboratory led to irreversible retinal damage.1 This finding soon was extended to other species, including rabbits2 and monkeys.3 Studies in animal models of retinal degeneration (eg, Royal College of Surgeons rats, ABCA4-mutant mice, or rhodopsin-mutant mice and dogs) have emphasized the interplay between the gene mutation and environmental light and demonstrated acceleration of the disease process by light.4- 10 The effect of environmental light on disease severity in humans with retinitis pigmentosa has been suggested by case reports,11 although definitive proof is lacking. However, patients with class B1 rhodopsin mutations may be at risk of accelerated vision loss with increased light exposures because they have defects in dark (bleaching) adaptation similar to those found in rhodopsin-mutant dogs that demonstrate a high susceptibility to retinal light damage.8,12,13 Many of the emerging therapies for retinal degeneration require the intraocular placement of a reagent or device with the use of an operating microscope.14,15 The damaging effect of the microscope light on the normal retina, even with the appropriate filtering of UV light, has been described previously,16,17 and there is increased emphasis on reducing the intensity and duration of the exposures. Herein, we describe a modification of an operating microscope with an infrared bandpass filter and a night-vision system to perform surgical interventions in the posterior segment of the eyes of rhodopsin-mutant dogs without the risk of photochemical retinal damage. This modification prevents acceleration of the photoreceptor degeneration that occurs with exposure to modest light levels as used in routine clinical practice.8 If humans with retinitis pigmentosa are shown to have similar light damage susceptibility, this microscope modification could be considered for surgical procedures such as the subretinal application of gene therapy vectors

Intravitreal Injection of Ciliary Neurotrophic Factor (CNTF) Causes Peripheral Remodeling and Does Not Prevent Photoreceptor Loss in Canine \u3cem\u3eRPGR\u3c/em\u3e Mutant Retina

Ciliary neurotrophic factor (CNTF) rescues photoreceptors in several animal models of retinal degeneration and is currently being evaluated as a potential treatment for retinitis pigmentosa in humans. This study was conducted to test whether CNTF prevents photoreceptor cell loss in XLPRA2, an early onset canine model of X-linked retinitis pigmentosa caused by a frameshift mutation in RPGR exon ORF15. Four different treatment regimens of CNTF were tested in XLPRA2 dogs. Under anesthesia, the animals received at different ages an intravitreal injection of 12 μg of CNTF in the left eye. The right eye served as a control and was injected with a similar volume of phosphate buffered saline (PBS). Ocular examinations were performed regularly during the treatment periods. At termination, the dogs were euthanatized, eyes collected and the retinas were processed for embedding in optimal cutting temperature (OCT) medium. The outer nuclear layer (ONL) thickness was evaluated on H&E sections and values in both CNTF- and PBS-treated eyes were compared. Morphologic alterations in the peripheral retina were characterized by immunohistochemistry using cell-specific markers. Cell proliferation in the retinas was examined on semi-thin plastic sections, and by BrdU pulse-labeling and Ki67 immunohistochemistry on cryosections. All CNTF-treated eyes showed early clinical signs of corneal epitheliopathy, subcapsular cataracts and uveitis. No statistically significant difference in ONL thickness was seen between the CNTF- and PBS-injected eyes. Prominent retinal remodeling that consisted in an abnormal increase in the number of rods, and in misplacement of some rods, cones, bipolar and Müller cells, was observed in the peripheral retina of CNTF-treated eyes. This was only seen when CNTF was in injected before the age at which the canine retina reaches full maturation. In XLPRA2 dogs, intravitreal injections of CNTF failed to prevent photoreceptors from undergoing cell death in the central and mid-peripheral retina. CNTF also caused ocular side-effects and morphologic alterations in the periphery that were consistent with cell dedifferentiation and proliferation. Our findings suggest that some inherited forms of retinal degeneration may not respond to CNTF\u27s neuroprotective effects

Identification of Genetic Variation and Haplotype Structure of the Canine \u3cem\u3eABCA4\u3c/em\u3e Gene for Retinal Disease Association Studies

Over 200 mutations in the retina specific member of the ATP-binding cassette transporter superfamily (ABCA4) have been associated with a diverse group of human retinal diseases. The disease mechanisms, and genotype–phenotype associations, nonetheless, remain elusive in many cases. As orthologous genes are commonly mutated in canine models of human blinding disorders, canine ABCA4 appears to be an ideal candidate gene to identify and study sequence changes in dogs affected by various forms of inherited retinal degeneration. However, the size of the gene and lack of haplotype assignment significantly limit targeted association and/or linkage approaches. This study assessed the naturally observed sequence diversity of ABCA4 in the dog, identifying 80% of novel variations. While none of the observed polymorphisms have been associated with blinding disorders to date, breed and potentially disease specific haplotypes have been identified. Moreover, a tag SNP map of 17 (15) markers has been established that accurately predicts common ABCA4 haplotypes (frequency \u3e 5%) explaining \u3e85% (\u3e80%) of the observed genetic diversity and will considerably advance future studies. Our sequence analysis of the complete canine ABCA4 coding region will clearly provide a baseline and tools for future association studies and comparative genomics to further delineate the role of ABCA4 in canine blinding disorders

Biology ideology and pastiche hegemony

As knowledge about the biological foundation of the modern patriarchal gender order is increasingly challenged within late-modern social worlds enclaves persist in which men and women can attempt to recreate understandings of the "natural" basis of sex difference. Within "Power Gym," male boxers were able to symbolize their bodies and behaviors in such a manner. The language and logic of popular scientific discourses authored and authorized notions of an "innate" manhood. The ability to instrumentally deploy one's manliness in symbolically legitimate ways could then be represented and emotionally experienced as a man's biological right and obligation. Through scripted performances of "mimetic" violence and self-bullying, the boxers were able to experience this discursive naturalness and carve out a masculinity-validating social enclave. As such, they accessed a "patriarchal dividend" by securing a local pastiche hegemony in which discourses surrounding men's natural place as physically and psychologically dominant remained largely uncontested. Through the reflexive appropriation of "science," within appropriate subcultural codes, these men could negotiate taboos and restrictions that are characteristic of late-modern social worlds. When considered in this way, the power of "scientific" truth claims to explain and justify a certain level of violence, aggression, and behaviors coded as masculine, comes to the fore

A Non-Stop S-Antigen Gene Mutation Is Associated With Late Onset Hereditary Retinal Degeneration in Dogs

Purpose: To identify the causative mutation of canine progressive retinal atrophy (PRA) segregating as an adult onset autosomal recessive disorder in the Basenji breed of dog. Methods: Basenji dogs were ascertained for the PRA phenotype by clinical ophthalmoscopic examination. Blood samples from six affected cases and three nonaffected controls were collected, and DNA extraction was used for a genome-wide association study using the canine HD Illumina single nucleotide polymorphism (SNP) array and PLINK. Positional candidate genes identified within the peak association signal region were evaluated. Results: The highest -Log10(P) value of 4.65 was obtained for 12 single nucleotide polymorphisms on three chromosomes. Homozygosity and linkage disequilibrium analyses favored one chromosome, CFA25, and screening of the S-antigen (SAG) gene identified a non-stop mutation (c.1216T\u3eC), which would result in the addition of 25 amino acids (p.*405Rext*25). Conclusions: Identification of this non-stop SAG mutation in dogs affected with retinal degeneration establishes this canine disease as orthologous to Oguchi disease and SAG-associated retinitis pigmentosa in humans, and offers opportunities for genetic therapeutic intervention

Bacterial resistance to arsenic protects against protist killing

Protists kill their bacterial prey using toxic metals such as copper. Here we hypothesize that the metalloid arsenic has a similar role. To test this hypothesis, we examined intracellular survival of Escherichia coli (E. coli) in the amoeba Dictyostelium discoideum (D. discoideum). Deletion of the E. coli ars operon led to significantly lower intracellular survival compared to wild type E. coli. This suggests that protists use arsenic to poison bacterial cells in the phagosome, similar to their use of copper. In response to copper and arsenic poisoning by protists, there is selection for acquisition of arsenic and copper resistance genes in the bacterial prey to avoid killing. In agreement with this hypothesis, both copper and arsenic resistance determinants are widespread in many bacterial taxa and environments, and they are often found together on plasmids. A role for heavy metals and arsenic in the ancient predator–prey relationship between protists and bacteria could explain the widespread presence of metal resistance determinants in pristine environments