The Neuroanatomical Organization of Projection Neurons Associated with Different Olfactory Bulb Pathways in the Sea Lamprey, Petromyzon marinus

Although there is abundant evidence for segregated processing in the olfactory system across vertebrate taxa, the spatial relationship between the second order projection neurons (PNs) of olfactory subsystems connecting sensory input to higher brain structures is less clear. In the sea lamprey, there is tight coupling between olfaction and locomotion via PNs extending to the posterior tuberculum from the medial region of the olfactory bulb. This medial region receives peripheral input predominantly from the accessory olfactory organ. However, the axons from olfactory sensory neurons residing in the main olfactory epithelium extend to non-medial regions of the olfactory bulb, and the non-medial bulbar PNs extend their axons to the lateral pallium. It is not known if the receptive fields of the PNs in the two output pathways overlap; nor has the morphology of these PNs been investigated. In this study, retrograde labelling was utilized to investigate the PNs belonging to medial and non-medial projections. The dendrites and somata of the medial PNs were confined to medial glomerular neuropil, and dendrites of non-medial PNs did not enter this territory. The cell bodies and dendrites of the non-medial PNs were predominantly located below the glomeruli (frequently deeper in the olfactory bulb). While PNs in both locations contained single or multiple primary dendrites, the somal size was greater for medial than for non-medial PNs. When considered with the evidence-to-date, this study shows different neuroanatomical organization for medial olfactory bulb PNs extending to locomotor control centers and non-medial PNs extending to the lateral pallium in this vertebrate

Input and output pathways of projection neurons in the sea lamprey olfactory bulb.

<p>These neuronal projections are based on Ren et al <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0069525#pone.0069525-Derjean1" target="_blank">[5]</a> and Derjean et al <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0069525#pone.0069525-Ren1" target="_blank">[10]</a>. The medial region of the olfactory bulb receives inputs from the accessory olfactory organ (AOO – blue) as well as sparse inputs from the main olfactory epithelium (MOE – orange). The medial projection neurons (green) project their axons to the posterior tuberculum (PT). The non-medial region of the olfactory bulb receives inputs from the main olfactory epithelium and the non-medial projection neurons (red) project their axons to the pallium. Red and green pipettes indicate location of biocytin insertion to retrogradely label projection neurons in the olfactory bulb (OB).</p

Distribution of medial and non-medial projection neurons.

<p>Rostral-caudal distribution of retrogradely labeled PNs in coronal sections of the young adult olfactory bulb following insertion of biocytin into the posterior tuberculum (A–C) or the lateral pallium (D–F). Biocytin insertion into the posterior tuberculum exclusively labelled medial PNs (A–C), while biocytin insertion into the lateral pallium labelled non-medial PNs (D–F). Scale bar, shown in A (125 µm) is the same for all images. Inset in C is a diagram of the olfactory bulb in the horizontal plane with lines representing the location of the coronal sections. Dashed lines in A–F outline the location of the medial glomerular neuropil. Arrows point to retrogradely labeled cell bodies.</p

Medial projection neurons are located within the glomerular layer.

<p>The axons of olfactory sensory neurons were labeled with <i>Griffonia simplicifolia</i> Lectin I, isolectin β4; (purple). The cell bodies (A–C) and dendrites (C) of retrogradely labelled medial PNs (green) are located within the glomerular neuropil. For non-medial retrogradely labeled PNs (red), the cell bodies were observed proximal (deep) to the glomerular layer (D–F), and dendrites projected into the non-medial glomeruli (E, F). Scale bars shown in A–F are 50 µm. Arrows point to retrogradely labelled cell bodies. Dashed lines denote the boundaries of glomeruli.</p

Morphometric characteristics of the olfactory bulb and projection neurons in young and spawning adult lamprey.

<p>Volume of olfactory bulb glomeruli, projection neuron (PN) cell counts, and the soma size of PNs in the olfactory bulb of young adult (post metamorphic) and spawning adult sea lamprey. All values are mean ± SEM. Sample size is indicated in brackets for each category.</p>†<p>denotes a statistically significant difference (p<0.05) between young adult and spawning adult lamprey while an asterisk.</p>*<p>denotes a statistically significant difference (p<0.001) between medial and non-medial PN soma size within a given life stage.</p

Response to putative round goby (Neogobius melanostomus) pheromones by centrarchid and percid fish species in the Laurentian Great Lakes

Pheromone trapping is an increasingly viable strategy to reduce invasive fish populations, largely due to the pheromones\u27 function of evoking behavioral responses among conspecifics. Prior to attempting such population control techniques, the pheromones must be identified and their possible influences on non-target species addressed. The round goby (Neogobius melanostomus) is a species invasive to the Great Lakes region, and negatively impacts the ecosystem by interfering with local fish populations. At least two 5β-reduced 3α-hydroxyl steroids released by reproductive N. melanostomus (11-O-ETIO and 11-O-ETIO-3s) evoke olfactory sensory responses from the olfactory epithelium of conspecifics, and water conditioned by reproductive males (containing these steroids) attracts female round gobies. In this study, we examined whether these putative pheromones, along with simultaneously-released 11-O-ETIO-17s, stimulate olfactory sensory responses from alternative fish species sharing the same ecosystem as N. melanostomus in the Great Lakes region. Rock bass (Ambloplites rupestris), bluegill sunfish (Lepomis macrochirus), pumpkinseed sunfish (Lepomis gibbosus), smallmouth bass (Micropterus dolomieu), and yellow perch (Perca flavescens) were the targets of an electro-olfactogram experiment designed to record responses to odors. When compared to round goby responses from previous studies, amino acids and the bile acid consistently elicited electro-olfactogram responses across all species, but only round gobies showed a response to the putative pheromones. This study supports the concept of conducting a pheromone trapping trial in the field without adversely affecting the olfactory responses of non-target fish in the area

Nutritional management of Eosinophilic Gastroenteropathies: Case series from the community

<p>Abstract</p> <p>Eosinophilic gastroenteropathies, such as eosinophilic esophagitis and eosinophilic colitis, have classically been treated with swallowed inhaled corticosteroids or oral corticosteroids. More recent studies have found elimination and elemental diets to be effective treatment alternatives to steroids. In this case series we describe the treatment of three children using nutritional management in a community setting. Elimination diets and elemental diets based on patch testing and skin prick tests reduced the eosinophil counts to normal levels in all three children. Food items which tested positive were then reintroduced while symptoms and eosinophil counts were monitored. Nutritional management of eosinophilic esophagitis and eosinophilic colitis was found to be effective in reducing symptoms. However, obstacles facing patients who choose this type of therapy include limitations due to the cost of repeated endoscopies, palatability of elimination/elemental diets and the availability of subspecialists trained in management (e.g. Allergy, Gastroenterology, and Pathology). It may be a worthwhile endeavour to overcome these obstacles as nutritional management minimizes the potential long-term effects of chronic steroid therapy.</p

The extent of intrauterine growth restriction determines the severity of cerebral injury and neurobehavioural deficits in rodents

<div><p>Background</p><p>Cerebral Palsy (CP) is the most common physical pediatric neurodevelopmental disorder and spastic diplegic injury is its most frequent subtype. CP results in substantial neuromotor and cognitive impairments that have significant socioeconomic impact. Despite this, its underlying pathophysiological mechanisms and etiology remain incompletely understood. Furthermore, there is a need for clinically relevant injury models, which a) reflect the heterogeneity of the condition and b) can be used to evaluate new translational therapies. To address these key knowledge gaps, we characterized a chronic placental insufficiency (PI) model, using bilateral uterine artery ligation (BUAL) of dams. This injury model results in intrauterine growth restriction (IUGR) in pups, and animals recapitulate the human phenotype both in terms of neurobehavioural and anatomical deficits.</p><p>Methods</p><p>Effects of BUAL were studied using luxol fast blue (LFB)/hematoxylin & eosin (H&E) staining, immunohistochemistry, quantitative Magnetic Resonance Imaging (MRI), and Catwalk neurobehavioural tests.</p><p>Results</p><p>Neuroanatomical analysis revealed regional ventricular enlargement and corpus callosum thinning in IUGR animals, which was correlated with the extent of growth restriction. Olig2 staining revealed reductions in oligodendrocyte density in white and grey matter structures, including the corpus callosum, optic chiasm, and nucleus accumbens. The caudate nucleus, along with other brain structures such as the optic chiasm, internal capsule, septofimbrial and lateral septal nuclei, exhibited reduced size in animals with IUGR. The size of the pretectal nucleus was reduced only in moderately injured animals. MAG/NF200 staining demonstrated reduced myelination and axonal counts in the corpus callosum of IUGR animals. NeuN staining revealed changes in neuronal density in the hippocampus and in the thickness of hippocampal CA2 and CA3 regions. Diffusion weighted imaging (DWI) revealed regional white and grey matter changes at 3 weeks of age. Furthermore, neurobehavioural testing demonstrated neuromotor impairments in animals with IUGR in paw intensities, swing speed, relative print positions, and phase dispersions.</p><p>Conclusions</p><p>We have characterized a rodent model of IUGR and have demonstrated that the neuroanatomical and neurobehavioural deficits mirror the severity of the IUGR injury. This model has the potential to be applied to examine the pathobiology of and potential therapeutic strategies for IUGR-related brain injury. Thus, this work has potential translational relevance for the study of CP.</p></div