We give explicit polynomial-sized (in n and k) semidefinite representations of the hyperbolicity cones associated with the elementary symmetric polynomials of degree k in n variables. These convex cones form a family of non-polyhedral outer approximations of the non-negative orthant that preserve low-dimensional faces while successively discarding high-dimensional faces. More generally we const...

Cone cells constitute only 3% of the photoreceptors of the wild-type (WT) mouse. While mouse rods have been thoroughly investigated with suction pipette recordings of their outer segment membrane currents, to date no recordings from WT cones have been published, likely because of the rarity of cones and the fragility of their outer segments. Recently, we characterized the photoreceptors of Nrl(...

The distribution of growth cones was studied in the optic nerve of monkeys during the first half of prenatal development using quantitative electron microscopic methods. Our aim was to test the hypothesis that ganglion cell growth cones extend predominantly along the surfaces of the nerve, just beneath the pia mater. A complete census of growth cones in cross sections of the nerve during the ea...

Light enters the eye, is focused by the cornea, passes through the variable-diameter iris, is further focused by the lens, and strikes the light-sensitive receptors of the retina in the back of the eye. The photoreceptors of the retina can be divided into two basic categories: rods and cones. At normal light levels, cones dominate the initial response to light, resulting in photopic vision. Thr...

NMDA receptors (NMDARs) are critical to the development of the nervous system, although their roles at axonal growth cones are unclear. We examined NMDAR localization and function at axonal growth cones of young hippocampal neurons. Our immunocytochemical data showed that native and transfected NMDAR subunits are expressed in axons and growth cones of young (days in vitro 3-6) hippocampal rat n...

We quantitatively analyzed several features of orthogradely labeled peripheral growth cones in the lumbosacral region of the chick embryo. We compared motoneuron growth cones in regions where they appear to express specific directional preferences (the plexus region and regions where muscle nerves diverge from main nerve trunks), which we operationally defined as "decision regions," to motoneur...