It is commonly assumed that the ultrastructural organization of the rim region of outer segment (OS) discs in rods and lamellae in cones requires functional retinal degeneration slow/rod outer segment membrane protein 1 (Rds/Rom-1) complexes. Cysteine-150 (C150) in Rds has been implicated in intermolecular disulfide bonding essential for functional Rds complexes. Transgenic mice containing the ...

Rod photoreceptors are specialized neurons that mediate vision in dim light and are the predominant photoreceptor type in nocturnal mammals. The rods of nocturnal mammals are unique among vertebrate cell types in having an 'inverted' nuclear architecture, with a dense mass of heterochromatin in the center of the nucleus rather than dispersed clumps at the periphery. To test if this unique nucle...

Cone photoreceptors are less sensitive to light and the duration of their photoresponse is shorter than that of rods. In salamander rods and cones, we identified 3 components in membrane currents activated by bright flashes of light: an early receptor current (ERC) resulting from charge displacement within visual pigments, a saturation photocurrent generated by the closure of the cGMP-sensitive...

Amphibian and mammalian rods can both detect single photons of light even though they differ greatly in physical dimensions, mammalian rods being much smaller in diameter than amphibian rods. To understand the changes in physiology and biochemistry required by such large differences in outer segment geometry, we developed a computational approach, taking into account the spatial organization of...

The retina's photoreceptor cells adjust their sensitivity to allow photons to be transduced over a wide range of light intensities. One mechanism thought to participate in sensitivity adjustments is Ca(2+) regulation of guanylate cyclase (GC) by guanylate cyclase-activating proteins (GCAPs). We evaluated the contribution of GCAPs to sensitivity regulation in rods by disrupting their expression ...

Mechanics is a fascinating field of physics. Its main purpose is to study the interaction of particles in the presence of forces such as gravity. In contrast to the dynamics of particles, the study of continuous media, such as elastic bodies, is challenging and still today not entirely well-understood. This is due to the fact that continuous media behave in numerous and complex ways. For exampl...

Introduction: Nowadays, the demand for CT-scan is increased, and this issue has become a critical subject in radiation protection, because of the risk of cancer especially for children. The quality assurance of CT images is a necessary factor that can effect on children dose. The CT dose index is an important dosimetry index in CT-Scan dosimetry. The purpose of this study is t...

Cone-driven responses of second-order retinal neurons are considerably faster than rod-driven responses. We examined whether differences in the kinetics of synaptic transmitter release from rods and cones may contribute to differences in postsynaptic response kinetics. Exocytosis from rods and cones was triggered by membrane depolarization and monitored in two ways: (1) by measuring EPSCs evoke...

We study the optimal packing of short, hard spherocylinders confined to lie tangential to a spherical surface, using simulated annealing and molecular dynamics simulations. For clusters of up to twelve particles, we map out the changes in the geometry of the closest-packed configuration as a function of the aspect ratio L/D, where L is the cylinder length and D the diameter of the rods. We find...

Histogenesis of the photoreceptor layer in the retina of goldfish was studied morphometrically and with thymidine radioautography at the light microscopic level. At hatching, the photoreceptor layer is poorly differentiated. The cells in the outer nuclear layer that are postmitotic' at hatching differentiate into cones. Two to 3 days after hatching, rod nuclei appear in the outer nuclear layer ...