Eleanor M. Josephson

Enhancement of Odorant-Induced Responses in Olfactory Receptor Neurons by Zinc Nanoparticles

Zinc metal nanoparticles in picomolar concentrations strongly enhance odorant responses of olfactory sensory neurons. One- to 2-nm metallic particles contain 40-300 zinc metal atoms, which are not in an ionic state. We exposed rat olfactory epithelium to metal nanoparticles and measured odorant responses by electroolfactogram and whole-cell patch clamp. A small amount of zinc nanoparticles added to an odorant or an extracellular/intracellular particle perfusion strongly increases the odorant response in a dose-dependent manner. Zinc nanoparticles alone produce no odor effects. Copper, gold, or silver nanoparticles do not produce effects similar to those of zinc. If zinc nanoparticles are replaced by Zn(+2) ions in the same concentration range, we observed a reduction of the olfactory receptor neuron odorant response. Based on these observations, we hypothesize that zinc nanoparticles are closely located to the interface between the guanine nucleotide-binding protein and the receptor proteins and are involved in transferring signals in the initial events of olfaction. Our results suggest that zinc metal nanoparticles can be used to enhance and sustain the initial olfactory events.

Selective cholinergic depletion in medial septum leads to impaired long term potentiation and glutamatergic synaptic currents in the hippocampus.

Cholinergic depletion in the medial septum (MS) is associated with impaired hippocampal-dependent learning and memory. Here we investigated whether long term potentiation (LTP) and synaptic currents, mediated by alpha-amino-3-hydroxy-5-methyl-isoxazole-4-propionate (AMPA) and N-methyl-D-aspartate (NMDA) receptors in the CA1 hippocampal region, are affected following cholinergic lesions of the MS. Stereotaxic intra-medioseptal infusions of a selective immunotoxin, 192-saporin, against cholinergic neurons or sterile saline were made in adult rats. Four days after infusions, hippocampal slices were made and LTP, whole cell, and single channel (AMPA or NMDA receptor) currents were recorded. Results demonstrated impairment in the induction and expression of LTP in lesioned rats. Lesioned rats also showed decreases in synaptic currents from CA1 pyramidal cells and synaptosomal single channels of AMPA and NMDA receptors. Our results suggest that MS cholinergic afferents modulate LTP and glutamatergic currents in the CA1 region of the hippocampus, providing a potential synaptic mechanism for the learning and memory deficits observed in the rodent model of selective MS cholinergic lesioning.

Structure and function of long-lived olfactory organotypic cultures from postnatal mice

The first synapse in the olfactory pathway mediates a significant transfer of information given the restricted association of specific olfactory receptor neurons with specific glomeruli in the olfactory bulb. To understand better how this connection is made and what the functional capacities of the participating cells are, we created a long‐lived culture system composed of olfactory epithelium and olfactory bulb tissues. Using the roller tube method of culturing, we grew epithelium‐bulb cocultures, explanted from 1–4‐day‐old Swiss Webster mice, on Aclar for periods ranging from 18 hr to 68 days. The explants flattened so that in some areas the culture was only a few cells thick, making individual cells distinguishable. From 107 cultures studied, we identified the following cell types by expression of specific markers (oldest culture expressing marker, days in vitro, DIV): olfactory receptor neurons (neural cell adhesion molecule, 42 DIV); mature receptor neurons (olfactory marker protein, 28 DIV); postmitotic olfactory receptor neurons and olfactory bulb neurons (β‐tubulin, 68 DIV); astrocytes (glial fibrillary acidic protein, glutamate/aspartate transporter, 68 DIV); olfactory horizontal basal cells (cytokeratin, 22 DIV). Neuronal processes formed glomeruli in 2–4‐week‐old cultures. We also recorded electro‐olfactography responses to puffs of vapor collected over an odorant mixture containing ethyl butyrate, eugenol, (+) carvone, and (−) carvone from cultures as old as 21 DIV. These features of our olfactory culture system make this model useful for studying properties of immature and mature olfactory receptor neurons, pathfinding strategies of receptor axons, and mechanisms of information transfer in the olfactory glomerulus.

High resolution MRI anatomy of the cat brain at 3 Tesla

BACKGROUND Feline models of neurologic diseases, such as lysosomal storage diseases, leukodystrophies, Parkinsons disease, stroke and NeuroAIDS, accurately recreate many aspects of human disease allowing for comparative study of neuropathology and the testing of novel therapeutics. Here we describe in vivo visualization of fine structures within the feline brain that were previously only visible post mortem. NEW METHOD 3Tesla MR images were acquired using T1-weighted (T1w) 3D magnetization-prepared rapid gradient echo (MPRAGE) sequence (0.4mm isotropic resolution) and T2-weighted (T2w) turbo spin echo (TSE) images (0.3mm×0.3mm×1mm resolution). Anatomic structures were identified based on feline and canine histology. RESULTS T2w high resolution MR images with detailed structural identification are provided in transverse, sagittal and dorsal planes. T1w MR images are provided electronically in three dimensions for unrestricted spatial evaluation. COMPARISON WITH EXISTING METHODS Many areas of the feline brain previously unresolvable on MRI are clearly visible in three orientations, including the dentate, interpositus and fastigial cerebellar nuclei, cranial nerves, lateral geniculate nucleus, optic radiation, cochlea, caudal colliculus, temporal lobe, precuneus, spinocerebellar tract, vestibular nuclei, reticular formation, pyramids and rostral and middle cerebral arteries. Additionally, the feline brain is represented in three dimensions for the first time. CONCLUSIONS These data establish normal appearance of detailed anatomical structures of the feline brain, which provide reference when evaluating neurologic disease or testing efficacy of novel therapeutics in animal models.

The lateral and medial compartments of the olfactory tubercle and their relation to olfactory-related input as determined by artificial neural network analysis

The current literature indicates that olfactory bulbar input projects throughout layer IA of the entire olfactory tubercle, with apparently more fibres in the lateral part than in the medial part of the tubercle. In addition, olfactory cortical association fibers project to layers IB, II, and III in all regions of the tubercle. This study exploited the phenomenon of transsynaptic transfer of WGA-HRP after injection into the olfactory bulb or rats to explore the degree of olfactory-related input to the tubercle. A computerized image analysis system was employed to quantify the amount of tracer transferred to layer II neurons of the tubercle. Qualitative analysis of the data indicates that the lateral tubercle consists of areas that receive little olfactory-related input. Nonparametric statistical tests and a novel application of artificial neural networks indicate regionally heterogeneous labeling across the tubercle and broad connections between homologous regions of the bulb and tubercle. These results have implications for understanding how olfactory sensory information is integrated into limbic-motor circuits by the olfactory tubercle.

Odorant Response Kinetics from Cultured Mouse Olfactory Epithelium at Different Ages in vitro

Mammalian olfactory epithelium can withstand the external environment, undergo life-long regeneration, and respond to thousands of odorant stimuli, making it an attractive system for a variety of studies. Previously, we described a long-lived olfactory coculture of olfactory epithelium and bulb tissues and we present here the kinetic properties of that culture system. Neonatal mouse epithelial-bulbar explants were grown for periods as long as 121 days in vitro (DIV), nearly doubling the survival time of our previously longest lived cultures. Cultures at all ages responded to air-borne odorants. The youngest cultures (1–15 DIV) showed shorter half-rise and half-decay times than older cultures (21–121 DIV), and were more variable in their half-decay times. Zinc nanoparticles enhanced electro-olfactogram responses of both younger and older cultures and both groups were immunopositive for olfactory marker protein. The results show that our olfactory culture model can support mature, odorant-responsive olfactory receptor neurons that possess many of the response features of in situ olfactory receptor neurons.

The inverted multilayer perceptron as a consistency measuring device in neuroanatomical image analysis

This protocol describes the use of optical imaging and artificial neural networks to analyze the complex patterns of transsynaptic transfer of WGA-HRP from olfactory bulbar axon terminals to olfactory tubercle projection neurons. This constitutes a unique application of neural networks to pattern recognition in a neuroanatomical tract-tracing study. Furthermore, the type of neural network used in this study, i.e., the inverted multilayer perceptron, possesses a novel construction that suits it for measuring consistency in data clusters. In the experiment described, the perceptron functioned as a consistency measuring device that revealed nonlinear relationships between the site of bulbar injection and the degree of regional labeling in the olfactory tubercle. Nonparametric statistical tests were used concurrently to validate the results of this previously untested form of the multilayer perceptron.

Contents Vol. 192, 2010

Stem Cells and Tissue Engineering S.F. Badylak, Pittsburgh, Pa. E-Mail: badylaks@msx.upmc.edu A. Müller, Würzburg E-Mail: albrecht.müller@mail.uni-wuerzburg.de L.E. Niklason, New Haven, Conn. E-Mail: laura.niklason@yale.edu A. Ratcliffe, San Diego, Calif. E-Mail: anthonyratcliffe@synthasome.com A.M. Wobus, Gatersleben E-Mail: wobusam@ipk-gatersleben.de Tumor Cell Plasticity E. Thompson, Melbourne E-Mail: rik@medstv.unimelb.edu.au