Purpose: To characterize the age-related accumulation of lipofuscin in a population of normal subjects, resolve differences in estimated accumulation rates obtained in previous studies, and characterize the spatial distribution of lipofuscin in the normal fundus.
Methods: Spectrophotometric measurements were made at the fovea and 7 degrees temporal to the fovea in 145 normal subjects (age range, 15-80 years). Spatial distribution along the four cardinal meridians was measured in selected subjects by both spectrophotometry and autofluorescence imaging. To minimize contributions of extraneous fluorophores, macular pigment, and melanin, all measurements used excitation at 550 nm, integrating emission between 650 and 750 nm.
Results: Lipofuscin fluorescence increased linearly until age 70, then declined. The rate of accumulation was significantly slower in the fovea than at the temporal site; accumulation rates in vivo were greater than previously observed in microscopic studies. Fluorescence was approximately 40% lower in the fovea than at 7 degrees eccentricity and was asymmetrically distributed around the fovea. The fluorescence was maximal at approximately 11 degrees temporally, approximately 7 degrees nasally, approximately 13 degrees superiorly, and approximately 9 degrees inferiorly. At the same eccentricity, fluorescence was always less along the inferior meridian than along any other.
Conclusions: Light absorption by RPE melanin can explain differences between the in vivo and ex vivo estimates of the rate of lipofuscin accumulation. Declining fluorescence at old age may represent removal of atrophic RPE cells. The spatial distribution of lipofuscin generally matches that of rods and reflects, rather than predicts, the pattern of age-related loss of rod photoreceptors.
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BMC Public Health
January 2025
Department of Statistics, University of South Africa, c/o Christiaan de Wet Road & Pioneer Avenue, Private Bag X6, Florida, 1710, Johannesburg, South Africa.
Background: The aim of this paper was to evaluate the distribution of HIV and TB in Ethiopia during four years (2015-2018) at the district level, considering both spatial and temporal patterns.
Methods: Consolidated data on the count of TB case notifications and the number of patients with HIV for four years, 2015-2018, were provided by the Ethiopian Federal Ministry of Health. The data was analyzed using the Bayesian hierarchical approach, employing joint spatiotemporal modelling.
Sci Rep
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Desautels Faculty of Management, McGill University, Montreal, QC, Canada.
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Yale School of the Environment, Yale University, New Haven, CT, USA.
Impending global urban population growth is expected to occur with considerable infrastructure expansion. However, our understanding of attendant infrastructure inequalities is limited, highlighting a critical knowledge gap in the sustainable development implications of urbanization. Using satellite data from 2000 to 2019, we examine country-level population-adjusted biases in infrastructure distribution within and between regions of varying urbanization levels and derive four key findings.
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Center for Theoretical Biological Physics, Rice University, Houston, Texas 77005, USA; Department of Chemistry, Rice University, Houston, Texas 77005, USA; Department of Chemical and Biomolecular Engineering, Rice University, Houston, Texas 77005, USA. Electronic address:
All living systems display remarkable spatial and temporal precision, despite operating in intrinsically fluctuating environments. It is even more surprising given that biological phenomena are regulated by multiple chemical reactions that are also random. While the underlying molecular mechanisms of surprisingly high precision in biology remain not well understood, a novel theoretical picture that relies on the coupling of relevant stochastic processes has been recently proposed and applied to explain different phenomena.
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ECOSPHERE, Department of Biology, University of Antwerp, Groenenborgerlaan 171, 2020 Antwerp, Belgium. Electronic address:
Metals are micropollutants of significant concern in the aquatic environment, requiring continuous monitoring to assess their distribution and environmental risk. This study investigated metals in water, sediment, and bivalves at different locations along the Scheldt estuary (the Netherlands-Belgium). The distribution of metals generally decreased from upstream to downstream in each matrix, with exceptions.
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