Takeshi Imai

In mammals, odorant receptors (ORs) direct the axons of olfactory sensory neurons (OSNs) toward targets in the olfactory bulb. We show that cyclic adenosine monophosphate (cAMP) signals that regulate the expression of axon guidance molecules are essential for the OR-instructed axonal projection. Genetic manipulations of ORs, stimulatory G protein, cAMP-dependent protein kinase, and cAMP response element–binding protein shifted the axonal projection sites along the anteriorposterior axis in the o

Sensory information detected by the peripheral nervous system is represented as a topographic map in the brain. It has long been thought that the topography of the map is determined by graded positional cues that are expressed by the target. Here, we analyzed the pre-target axon sorting for olfactory map formation in mice. In olfactory sensory neurons, an axon guidance receptor, Neuropilin-1, and its repulsive ligand, Semaphorin-3A, are expressed in a complementary manner. We found that expressi

Sensory systems must map accurate representations of the external world in the brain. Although the physical senses of touch and vision build topographic representations of the spatial coordinates of the body and the field of view, the chemical sense of olfaction maps discontinuous features of chemical space, comprising an extremely large number of possible odor stimuli. In both mammals and insects, olfactory circuits are wired according to the convergence of axons from sensory neurons expressing

Recent studies using molecular genetics, electrophysiology, in vivo imaging, and behavioral analyses have elucidated detailed connectivity and function of the mammalian olfactory circuits. The olfactory bulb is the first relay station of olfactory perception in the brain, but it is more than a simple relay: olfactory information is dynamically tuned by local olfactory bulb circuits and converted to spatiotemporal neural code for higher-order information processing. Because the olfactory bulb pro

Sensory information is selectively or non-selectively enhanced and inhibited in the brain, but it remains unclear whether and how this occurs at the most peripheral level. Using in vivo calcium imaging of mouse olfactory bulb and olfactory epithelium in wild-type and mutant animals, we show that odors produce not only excitatory but also inhibitory responses in olfactory sensory neurons (OSNs). Heterologous assays indicate that odorants can act as agonists to some but inverse agonists to other o

During the development of the nervous system, neurons often connect axons and dendrites over long distances, which are navigated by chemical cues. During the past few decades, studies on axon guidance have focused on chemical cues provided by the axonal target or intermediate target. However, recent studies have shed light on the roles and mechanisms underlying axon-axon interactions during neuronal circuit assembly. The roles of axon-axon interactions are best exemplified in recent studies on o

In developing brains, activity-dependent remodeling facilitates the formation of precise neuronal connectivity. Synaptic competition is known to facilitate synapse elimination; however, it has remained unknown how different synapses compete with one another within a post-synaptic cell. Here, we investigate how a mitral cell in the mouse olfactory bulb prunes all but one primary dendrite during the developmental remodeling process. We find that spontaneous activity generated within the olfactory

Abstract Investigations with the electron microscope on γ-irradiated single crystals of LiH have revealed the presence of cubic voids, or bubbles. These bubbles are crystallographically oriented, principally with their sides parallel to the (100) planes of the LiH crystals. Bubbles range in size from ∼ 75 Å to ∼ 1500 Å. Average bubble size increases with increasing irradiation dose and irradiation temperature, with temperature affecting size the most, by far. These bubbles are believed to be res

Reports 727 hydroxyproline level when the alkaline phosphatase level is of the order found in this patient. Further evidence of normal bone metabolism was obtained from the normal hydroxyproline excretion. There was no laboratory evidence to suggest hyperpara- thyroidism.

Developing neurons initially form excessive neurites and then remodel them based on molecular cues and neuronal activity. Developing mitral cells in the olfactory bulb initially extend multiple primary dendrites. They then stabilize single primary dendrites while eliminating others. However, the mechanisms underlying selective dendrite remodeling remain elusive. Using CRISPR-Cas9-based knockout screening combined with in utero electroporation, we identify BMPR-2 as a key regulator for selective

After spinal cord injury (SCI), secondary injury results in an expanding area of glial cell apoptosis. Oligodendrocyte precursor cells (OPCs) actively proliferate after SCI, but many of these cells undergo apoptosis. One of the factors that exacerbates secondary injury is endoplasmic reticulum (ER) stress. In this study, we tested the effects of amiloride treatment on the fate of OPCs during secondary injury in rats. Amiloride is an FDA-approved diuretic for treating hypertension, which in rats