Visual and Ocular Manifestations of Alzheimer's Disease and Their Use as Biomarkers for Diagnosis and Progression

Alzheimer's disease (AD) is the most common form of dementia affecting the growing aging population today, with prevalence expected to rise over the next 35 years. Clinically, patients exhibit a progressive decline in cognition, memory, and social functioning due to deposition of amyloid β (Aβ) protein and intracellular hyperphosphorylated tau protein. These pathological hallmarks of AD are measured either through neuroimaging, cerebrospinal fluid analysis, or diagnosed post-mortem. Importantly, neuropathological progression occurs in the eye as well as the brain, and multiple visual changes have been noted in both human and animal models of AD. The eye offers itself as a transparent medium to cerebral pathology and has thus potentiated the development of ocular biomarkers for AD. The use of non-invasive screening, such as retinal imaging and visual testing, may enable earlier diagnosis in the clinical setting, minimizing invasive and expensive investigations. It also potentially improves disease management and quality of life for AD patients, as an earlier diagnosis allows initiation of medication and treatment. In this review, we explore the evidence surrounding ocular changes in AD and consider the biomarkers currently in development for early diagnosis

Morpho-physiological and micrographic characterization of maize hybrids under NaCl and Cd stress

A hydroponic experiment was conducted to investigate single and combined effects of 5 µmol/L Cd and 100 mM NaCl on growth, root morphology, photosynthetic parameters, leaf and root ultra-structure of two maize hybrids (26204 and 8441) differing in salt tolerance. A more pronounced reduction on growth, root morphology, SPAD value, chlorophyll fluorescence and leaf gas exchange indicated that 8441 was more sensitive than 26204 to both Cd and NaCl stresses. Transmission electron microscopy of 8441 revealed a more severe destruction in root and leaf cells as compared to 26204. The reduction in growth and photosynthetic parameters were associated with severe disorganization of nucleus, chloroplast, mitochondrial damage, vacuolation, and increased number and size of pastoglobuli. Interestingly, the combined stress of both NaCl and Cd had obvious beneficial effect on the plant growth, photosynthetic parameters and cell ultra-structure relative to Cd or Na stress alone in the two maize hybrids. The study suggested that there is involvement of same genetic and physiological mechanisms in response to both Cd and NaCl stresses