Modelling the signal delivered by a population of first-order neurons in a moth olfactory system

A statistical model of the population of first-order olfactory receptor neurons (ORNs) is proposed and analysed. It describes the relationship between stimulus intensity (odour concentration) and coding variables such as rate and latency of the population of several thousand sex-pheromone sensitive ORNs in male moths. Although these neurons likely express the same olfactory receptor, they exhibit, at any concentration, a relatively large heterogeneity of responses in both peak firing frequency and latency of the first action potential fired after stimulus onset. The stochastic model is defined by a multivariate distribution of six model parameters that describe the dependence of the peak firing rate and the latency on the stimulus dose. These six parameters and their mutual linear correlations were estimated from experiments in single ORNs and included in the multidimensional model distribution. The model is utilized to reconstruct the peak firing rate and latency of the message sent to the brain by the whole ORN population at different stimulus intensities and to establish their main qualitative and quantitative properties. Finally, these properties are shown to be in agreement with those found previously in a vertebrate ORN population

An Expressed Sequence Tag collection from the male antennae of the Noctuid moth Spodoptera littoralis: a resource for olfactory and pheromone detection research

<p>Abstract</p> <p>Background</p> <p>Nocturnal insects such as moths are ideal models to study the molecular bases of olfaction that they use, among examples, for the detection of mating partners and host plants. Knowing how an odour generates a neuronal signal in insect antennae is crucial for understanding the physiological bases of olfaction, and also could lead to the identification of original targets for the development of olfactory-based control strategies against herbivorous moth pests. Here, we describe an Expressed Sequence Tag (EST) project to characterize the antennal transcriptome of the noctuid pest model, <it>Spodoptera littoralis</it>, and to identify candidate genes involved in odour/pheromone detection.</p> <p>Results</p> <p>By targeting cDNAs from male antennae, we biased gene discovery towards genes potentially involved in male olfaction, including pheromone reception. A total of 20760 ESTs were obtained from a normalized library and were assembled in 9033 unigenes. 6530 were annotated based on BLAST analyses and gene prediction software identified 6738 ORFs. The unigenes were compared to the <it>Bombyx mori </it>proteome and to ESTs derived from Lepidoptera transcriptome projects. We identified a large number of candidate genes involved in odour and pheromone detection and turnover, including 31 candidate chemosensory receptor genes, but also genes potentially involved in olfactory modulation.</p> <p>Conclusions</p> <p>Our project has generated a large collection of antennal transcripts from a Lepidoptera. The normalization process, allowing enrichment in low abundant genes, proved to be particularly relevant to identify chemosensory receptors in a species for which no genomic data are available. Our results also suggest that olfactory modulation can take place at the level of the antennae itself. These EST resources will be invaluable for exploring the mechanisms of olfaction and pheromone detection in <it>S. littoralis</it>, and for ultimately identifying original targets to fight against moth herbivorous pests.</p

L'organe septal de Masera et le ganglion de Grueneberg

ISBN-10 : 978-2-7592-1770-0 ; issn : 1777-462

Perception périphérique des signaux sensoriels. 1- Olfaction

Poste

Accurate Estimation of Bicarbonate and Acetic Acid Concentrations with Wider Ranges in Anaerobic Media Using Classical FOS/TAC Titration Method

International audienceThe determination of a volatile fatty acid content (FOS) and total alkalinity (TAC) can be carried out using Nordmann’s FOS/TAC titration method developed in the 1970s. This two-point titration (pH = 5 and 4.4) can be simply implemented and is widely employed by both the academic and industrial worlds. However, the present study proves that Nordmann’s method is only valid in limited ranges, since the titration of one FOS and TAC has an impact on the determination of the other, especially in extreme conditions. The present work develops a numerical tool with Scilab simulating the acid–base equilibria of titration. The program is efficient in predicting the experimental equivalent volumes obtained from Nordmann’s method with different combinations of sodium acetate and sodium bicarbonate contents. The mean absolute percentage errors (MAPE) between the simulation and experiment are below 7%. Two new formulas are developed, considering both equivalent volumes at pH = 5 and 4.4 to calibrate FOS and TAC values. The proposed formulas show their good performance in predicting various combinations of FOS and TAC contents in an anaerobic digestate at TAC ranging from 0 to 20,000 mg CaCO3·L−1 and FOS ranging from 0 to 31,000 mg HAc·L−1

Underestimation of Dry Matter of Anaerobic Media with High Bicarbonate Concentration

International audienc

Centrifugal projections to the main olfactory bulb revealed by trans‐synaptic retrograde tracing in mice

International audienceA wide range of evidence indicates that olfactory perception is strongly involved in food intake. However, the polysynaptic circuitry linking the brain areas involved in feeding behaviour to the olfactory regions is not well-known. The aim of this paper was to examine such circuits. Thus, we described, using hodological tools such as trans-synaptic viruses (PRV152) transported in a retrograde manner, the long-distance indirect projections (2-3 synapses) onto the main olfactory bulb (MOB). The b-subunit of the cholera toxin (CTb) which is a monosynaptic retrograde tracer was used as a control to be able to differentiate between direct and indirect projections. Our tracing experiments showed that the arcuate nucleus of the hypothalamus, as a major site for regulation of food intake, sends only very indirect projections onto the MOB. Indirect projections to MOB also originate from the solitary nucleus which is involved in energy homeostasis. Other indirect projections have been evidenced in areas of the reward circuit such as VTA and accumbens nucleus. In contrast, direct projections to the MOB arise from MCH- and Orx neurons in the lateral hypothalamus. Functional significances of these projections are discussed in relation to the role of food odors in feeding and reward-related behavior

Study protocol on Alzheimer’s disease and related disorders: focus on clinical and imaging predictive markers in co-existing lesions

Abstract Background One of the crucial challenges for the future of therapeutic approaches to Alzheimer’s disease (AD) is to target the main pathological processes responsible for disability and dependency. However, a progressive cognitive impairment occurring after the age of 70, the main population affected by dementia, is often related to mixed lesions of neurodegenerative and vascular origins. Whereas young patients are mostly affected by pure lesions, ageing favours the occurrence of co-lesions of AD, cerebrovascular disease (CVD) and Lewy body dementia (LBD). Most of clinical studies report on functional and clinical disabilities in patients with presumed pure pathologies. But, the weight of co-morbid processes involved in the transition from an independent functional status to disability in the elderly with co-lesions still remains to be elucidated. Neuropathological examination often performed at late stages cannot answer this question at mild or moderate stages of cognitive disorders. Brain MRI, Single Photon Emission Computed Tomography (SPECT) with DaTscan®, amyloid Positron Emission Tomography (PET) and CerebroSpinal Fluid (CSF) AD biomarkers routinely help in performing the diagnosis of underlying lesions. The combination of these measures seems to be of incremental value for the diagnosis of mixed profiles of AD, CVD and LBD. The aim is to determine the clinical, neuropsychological, neuroradiological and biological features the most predictive of cognitive, behavioral and functional impairment at 2 years in patients with co-existing lesions. Methods A multicentre and prospective cohort study with clinical, neuro-imaging and biological markers assessment will recruit 214 patients over 70 years old with a cognitive disorder of AD, cerebrovascular and Lewy body type or with coexisting lesions of two or three of these pathologies and fulfilling the diagnostic criteria for dementia at a mild to moderate stage. Patients will be followed every 6 months (clinical, neuropsychological and imaging examination and collection of cognitive, behavioural and functional impairment) for 24 months. Discussion This study aims at identifying the best combination of markers (clinical, neuropsychological, MRI, SPECT-DaTscan®, PET and CSF) to predict disability progression in elderly patients presenting coexisting patterns. Trial registration NCT02052947

Impact of Cognitive, Functional, Behavioral Disorders, and Caregiver Burden on the Risk of Nursing Home Placement

International audienceObjectives: To estimate the attributable fraction of nursing home placement associated with cognitive impairment, neuropsychiatric symptoms, behavioral disorders, functional limitations, and caregiver burden.Design: Longitudinal study conducted on the "MEMORA cohort" linked with both regional public health insurance and hospital discharge databases.Setting: Memory center at the University Hospital of Lyon, France.Participants: A sample of 2456 outpatients attending the memory center between 2012 and 2017.Measures: Cognitive impairment, functional limitations, neuropsychiatric symptoms/behavioral disorders, and caregiver burden were measured with the Mini-Mental State Examination, the Instrumental Activities of Daily Living scale, the Neuropsychiatric Inventory (NPI), and a short version of the Zarit Burden Inventory, respectively. Sociodemographics characteristics were collected during the first visit. Comorbidities were gathered from the hospital discharge database. Dates of nursing home placement were obtained from the public health insurance database.Results: More than 38% of nursing home placements were attributable to caregiver burden, and the attributable fraction associated with functional limitations exceeded 35%. Between 20% and 25% of nursing home placements were due to cognitive impairment whereas less than 16% were attributable to neuropsychiatric symptoms or behavioral disorders. The associations between anxiety or agitation and nursing home placement were mediated by caregiver burden. Apathy or aberrant motor behaviors were associated with a higher risk of nursing home placement independently of caregiver burden.Conclusions/implications: Our findings suggest that a high proportion of nursing home placements are attributable to caregiver burden and functional limitations in outpatients attending a memory center. Cognitive impairment and neuropsychiatric symptoms or behavioral disorders contribute less to nursing home placements. Interventions directed to delay nursing home placement should emphasize actions toward reducing caregiver burden and functional limitations of patients

Experience-dependent modulation of antennal sensitivity and input to antennal lobes in male moths (Spodoptera littoralis) pre-exposed to sex pheromone

International audienceSex pheromones are intraspecific olfactory signals emitted by one sex to attract a potential mating partner. Behavioural responses to sex pheromones are generally highly stereotyped. However, they can be modulated by experience, as male moths previously exposed to female sex pheromone respond with a lower threshold upon further detection, even after long delays. Here, we address the question of the neural mechanisms underlying such long-term modulation. As previous work has shown increased responses to pheromone in central olfactory neurons, we asked whether brief exposure to the pheromone increases input activity from olfactory receptor neurons. Males pre-exposed to sex pheromone exhibited increased peripheral sensitivity to the main pheromone component. Among nine antennal genes targeted as putatively involved in pheromone reception, one encoding a pheromone-binding protein showed significant upregulation upon exposure. In the primary olfactory centre (antennal lobe), the neural compartment processing the main pheromone component was enlarged after a brief pheromone exposure, thus suggesting enduring structural changes. We hypothesise that higher peripheral sensitivity following pre-exposure leads to increased input to the antennal lobe, thus contributing to the structural and functional reorganization underlying a stable change in behaviour