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  • 1
    ISSN: 1432-0568
    Keywords: Key words Photoreceptor ; Nearest neighbor analysis ; Nyquist limit ; Aliasing ; Aging ; Sex differences
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  We have analyzed variation in the structure of the human photoreceptor mosaic as a function of age, sex, and retinal location using the nearest neighbor and density recovery profile methods. In contrast to most previous work, we have focused our analysis on the mid- and far-peripheral human retina. Video-enhanced differential interference contrast optics was used to characterize differences in the nasal and temporal periphery of unstained wholemounts from 12 males and 12 females ranging in age from 15- to 83-years-old. At sites matched for cone density (∼5,000 cones/mm2), the mosaic is far more orderly in the temporal than in the nasal periphery. This is true at all ages and in both sexes. Despite their increased local order, regularity ratios of adjacent temporal fields tend to be much more variable than are those of adjacent nasal fields. These marked nasal-temporal differences are eliminated when eccentricity is held constant and cone density is allowed to vary. There is a mild, statistically significant age-related decline in the regularity of the cone mosaic, but only in the nasal periphery. There are no significant differences in the precision of the cone mosaic between sexes. The equivalence of the regularity of the mosaic at matched eccentricities, but not at matched cone densities, suggests that the irregularity of the mosaic is secondary to developmental gradients and, more generally, to reduced selection for high acuity vision in the retinal periphery.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Science Ltd
    Scandinavian journal of immunology 54 (2001), S. 0 
    ISSN: 1365-3083
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Understanding of the genetic basis of normal and abnormal development of the immune response is an enormous undertaking. The immune response, at the most minimal level, involves interactions of antigen presenting cells (APCs), T and B cells. Each of these cells produce cell surface and soluble factors (cytokines) that affect both autocrine and paracrine functions. A second level of complexity needs to consider the development of the macrophage/monocyte lineage as well as the production of the common lymphoid precursor which undergoes distinct maturation steps in the thymus and periphery to form mature T cells as well as in BM (BM) and lymphoid organs to form mature B cells. A third level of complexity involves the immune response to infectious agents including viruses and also the response to tumour antigens. In addition, there are imbalances that predispose to decreased responses (immunodeficiencies) or increased responses (autoimmunity). A fourth level of complexity involves attempts to understand the differences in the immune response that occurs at a very young age, in adults, and at a very old age. This review will focus on the use of C57BL/6 J X DBA/2 J (BXD) recombinant inbred (RI) strains of mice to map genetic loci associated with the production of lymphoid precursors in the BM, development of T cells in the thymus, and T-cell responses to stimulation in the peripheral lymphoid organs in adult and in aged mice. Strategies to improve the power and precision in which complex traits such as the age-related immune response can be mapped is limited with the current set of 35 strains of BXD mice. Strategies to increase these strains by generating recombinant intercross (RIX) strains of mice are being developed to enable this large set of lines to detect quantitative trait loci (QTLs) with a much higher consistency and statistical power. More importantly, the resolution with which these QTLs can be mapped would be greatly improved and, in many cases, adequate to carry out direct identification of candidate genes. It is likely that, given the complexity of the immune system development, the number of cells involved in an immune response, and especially the changes in the immune system with ageing, mapping hundreds of genes will be required to fully understand age-related changes in the immune response. This review outlines ongoing and future strategies that will enable the mapping and identification of these genes.
    Type of Medium: Electronic Resource
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