Calcium Homeostasis and Cone Signaling Are Regulated by Interactions between Calcium Stores and Plasma Membrane Ion Channels

Calcium is a messenger ion that controls all aspects of cone photoreceptor function, including synaptic release. The dynamic range of the cone output extends beyond the activation threshold for voltage-operated calcium entry, suggesting another calcium influx mechanism operates in cones hyperpolarized by light. We have used optical imaging and whole-cell voltage clamp to measure the contribution of store-operated Ca2+ entry (SOCE) to Ca2+ homeostasis and its role in regulation of neurotransmission at cone synapses. Mn2+ quenching of Fura-2 revealed sustained divalent cation entry in hyperpolarized cones. Ca2+ influx into cone inner segments was potentiated by hyperpolarization, facilitated by depletion of intracellular Ca2+ stores, unaffected by pharmacological manipulation of voltage-operated or cyclic nucleotide-gated Ca2+ channels and suppressed by lanthanides, 2-APB, MRS 1845 and SKF 96365. However, cation influx through store-operated channels crossed the threshold for activation of voltage-operated Ca2+ entry in a subset of cones, indicating that the operating range of inner segment signals is set by interactions between store- and voltage-operated Ca2+ channels. Exposure to MRS 1845 resulted in ∼40% reduction of light-evoked postsynaptic currents in photopic horizontal cells without affecting the light responses or voltage-operated Ca2+ currents in simultaneously recorded cones. The spatial pattern of store-operated calcium entry in cones matched immunolocalization of the store-operated sensor STIM1. These findings show that store-operated channels regulate spatial and temporal properties of Ca2+ homeostasis in vertebrate cones and demonstrate their role in generation of sustained excitatory signals across the first retinal synapse

Investigating the Challenges Facing Mentally Retarded Adolescents in Acquiring Self-Empowerment Skills

Background and Aim: Disability is a global phenomenon that has been discussed in all societies throughout history, so that 10% of the world's population is physically, mentally, psychologically, and socially disabled according to the World Health Organization (WHO). So, officials and macro-policymakers in the field of the disabled should provide appropriate conditions to promote the mental health of families with children with special disabilities by taking the necessary measures. Accordingly, this study was conducted to identify the challenges facing mentally retarded adolescents in acquiring self-empowerment skills. Methods: This is a qualitative study based on the nature of the data and a baseline study in terms of the type of theory. The statistical population included specialists and practitioners working in centers for the education and care of mentally retarded adolescents, mothers, and caregivers who were selected by purposive sampling in Tehran in 2019. Data were collected through semi-structured 35- to 45-minute interviews to reach saturation with 15 specialists and 10 mothers and caregivers. Data were analyzed by the method developed by Strauss and Corbin. Results: According to the results, the challenges in acquiring self-empowerment skills in mentally retarded adolescents could be classified as parental ignorance, rejection, economic, social, and family constraints, abuse/harassment, feelings of inadequacy, inefficiency, Inadequate professional and welfare support, social inequality, lack of enforcement of laws, lack of jobs concerning disability, educational malfunctions, and lack of qualified trainers. Conclusion: The results showed that a lack of awareness of the abilities and potentials of mentally retarded adolescents in acquiring self-empowerment skills creates challenges for them to achieve this goal. So, special attention should be paid to mentally retarded adolescents and careful consideration of the challenges they face in acquiring self-improvement skills. This can lead to solutions to increase their social skills, life skills, and self-empowerment