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Diego Restrepo

Publications and source records attributed to Diego Restrepo.

16 recordsLinked to original sources
PubMed2022

Signatures for viral infection and inflammation in the proximal olfactory system in familial Alzheimer's disease.

Alzheimer's disease (AD) is characterized by deficits in olfaction and olfactory pathology preceding diagnosis of dementia. Here we analyzed differential gene and protein expression in the olfactory bulb (OB) and tract (OT) of familial AD (FAD) individuals carrying the autosomal dominant presenilin 1 E280A mutation. Compared to control, FAD OT had increased immunostaining for β-amyloid (Aβ) and CD68 in high and low myelinated regions, as well as increased immunostaining for Iba1 in the high myelinated region. In FAD samples, RNA sequencing showed: (1) viral infection in the OB; (2) inflammation in the OT that carries information via entorhinal cortex from the OB to hippocampus, a brain region essential for learning and memory; and (3) decreased oligodendrocyte deconvolved transcripts. Interestingly, spatial proteomic analysis confirmed altered myelination in the OT of FAD individuals, implying dysfunction of communication between the OB and hippocampus. These findings raise the possibility that viral infection and associated inflammation and dysregulation of myelination of the olfactory system may disrupt hippocampal function, contributing to acceleration of FAD progression.

Humans↗
PubMed2006

Toward a self-deploying shape memory polymer neuronal electrode.

The widespread application of neuronal probes for chronic recording of brain activity and functional stimulation has been slow to develop partially due to long-term biocompatibility problems with existing metallic and ceramic probes and the tissue damage caused during probe insertion. Stiff probes are easily inserted into soft brain tissue but cause astrocytic scars that become insulating sheaths between electrodes and neurons. In this communication, we explore the feasibility of a new approach to the composition and implantation of chronic electrode arrays. We demonstrate that softer polymer-based probes can be inserted into the olfactory bulb of a mouse and that slow insertion of the probes reduces astrocytic scarring. We further present the development of a micromachined shape memory polymer probe, which provides a vehicle to self-deploy an electrode at suitably slow rates and which can provide sufficient force to penetrate the brain. The deployment rate and composition of shape memory polymer probes can be tailored by polymer chemistry and actuator design. We conclude that it is feasible to fabricate shape memory polymer-based electrodes that would slowly self-implant compliant conductors into the brain, and both decrease initial trauma resulting from implantation and enhance long-term biocompatibility for long-term neuronal measurement and stimulation.

Algorithms↗
PubMed2006

Odortypes and MHC peptides: Complementary chemosignals of MHC haplotype?

The olfactory and immune systems must perform optimally in the task of recognizing thousands of molecules to ensure survival. A particularly intriguing link between these systems is that animals can smell differences in the major histocompatibility complex (MHC), a cluster of highly polymorphic genes found on human chromosome 6 and mouse chromosome 17. Two different sets of compounds found in urine have been postulated to convey information on MHC haplotype: volatile compounds (odortypes) and MHC peptides. Here we argue for complementary roles for these chemosignals.

Animals↗
PubMed2006

Ultrastructural localization of connexins (Cx36, Cx43, Cx45), glutamate receptors and aquaporin-4 in rodent olfactory mucosa, olfactory nerve and olfactory bulb.

Odorant/receptor binding and initial olfactory information processing occurs in olfactory receptor neurons (ORNs) within the olfactory epithelium. Subsequent information coding involves high-frequency spike synchronization of paired mitral/tufted cell dendrites within olfactory bulb (OB) glomeruli via positive feedback between glutamate receptors and closely-associated gap junctions. With mRNA for connexins Cx36, Cx43 and Cx45 detected within ORN somata and Cx36 and Cx43 proteins reported in ORN somata and axons, abundant gap junctions were proposed to couple ORNs. We used freeze-fracture replica immunogold labeling (FRIL) and confocal immunofluorescence microscopy to examine Cx36, Cx43 and Cx45 protein in gap junctions in olfactory mucosa, olfactory nerve and OB in adult rats and mice and early postnatal rats. In olfactory mucosa, Cx43 was detected in gap junctions between virtually all intrinsic cell types except ORNs and basal cells; whereas Cx45 was restricted to gap junctions in sustentacular cells. ORN axons contained neither gap junctions nor any of the three connexins. In OB, Cx43 was detected in homologous gap junctions between almost all cell types except neurons and oligodendrocytes. Cx36 and, less abundantly, Cx45 were present in neuronal gap junctions, primarily at "mixed" glutamatergic/electrical synapses between presumptive mitral/tufted cell dendrites. Genomic analysis revealed multiple miRNA (micro interfering RNA) binding sequences in 3'-untranslated regions of Cx36, Cx43 and Cx45 genes, consistent with cell-type-specific post-transcriptional regulation of connexin synthesis. Our data confirm absence of gap junctions between ORNs, and support Cx36- and Cx45-containing gap junctions at glutamatergic mixed synapses between mitral/tufted cells as contributing to higher-order information coding within OB glomeruli.

Animals↗
PubMed2005

Evaluation of the validity of a maximum likelihood adaptive staircase procedure for measurement of olfactory detection threshold in mice.

Threshold is defined as the stimulus intensity necessary for a subject to reach a specified percent correct on a detection test. MLPEST (maximum likelihood parameter estimation by sequential testing) is a method that is able to determine threshold accurately and more rapidly than many other methods. Originally developed for human auditory and visual tasks, it has been adapted for human olfactory and gustatory tests. In order to utilize this technique for olfactory testing in mice, we have adapted MLPEST methodology for use with computerized olfactometry as a tool to estimate odor detection thresholds. Here we present Monte Carlo simulations and operant conditioning data that demonstrate the potential utility of this technique in mice, we explore the ramifications of altering MLPEST test parameters on performance, and we discuss the advantages and disadvantages of using MLPEST compared to other methods for the estimation of thresholds in rodents. Using MLPEST, we find that olfactory detection thresholds in mice deficient for the cyclic nucleotide-gated channel subunit A2 are similar to those of wild-type animals for odorants the knockout animals are able to detect.

Animals↗
PubMed2005

Simultaneous activation of mouse main and accessory olfactory bulbs by odors or pheromones.

It is generally believed that the main olfactory system processes common odors and the accessory olfactory system is specifically for pheromones. The potential for these two systems to respond simultaneously to the same stimuli has not been fully explored due to methodological limitations. Here we examine this phenomenon using high-resolution functional magnetic resonance imaging (fMRI) to reveal simultaneously the responses in the main (MOB) and accessory olfactory bulbs (AOB) to odors and pheromones. Common odorants elicited strong signals in the MOB and weak signals in the AOB. 2-Heptanone, a known mouse pheromone, elicited strong signals in both the MOB and AOB. Urine odor, a complicated mixture of pheromones and odorants, elicited significant signals in limited regions of the MOB and large regions of the AOB. The fMRI results demonstrate that both the main and the accessory olfactory systems may respond to volatile compounds but with different selectivity, suggesting a greater integration of the two olfactory pathways than traditionally believed.

Animals↗
PubMed2005

Analysis of training-induced changes in ethyl acetate odor maps using a new computational tool to map the glomerular layer of the olfactory bulb.

Odor quality is thought to be encoded by the activation of partially overlapping subsets of glomeruli in the olfactory bulb (odor maps). Mouse genetic studies have demonstrated that olfactory sensory neurons (OSNs) expressing a particular olfactory receptor target their axons to a few individual glomeruli in the bulb. While the specific targeting of OSN axons provides a molecular underpinning for the odor maps, much remains to be understood about the relationship between the functional and molecular maps. In this article, we ask the question whether intensive training of mice in a go/no-go operant conditioning odor discrimination task affects odor maps measured by determining c-fos up-regulation in periglomerular cells. Data analysis is performed using a newly developed suite of computational tools designed to systematically map functional and molecular features of glomeruli in the adult mouse olfactory bulb. This suite provides the necessary tools to process high-resolution digital images, map labeled glomeruli, visualize odor maps, and facilitate statistical analysis of patterns of identified glomeruli in the olfactory bulb. The software generates odor maps (density plots) based on glomerular activity, density, or area. We find that training up-regulates the number of glomeruli that become c-fos positive after stimulation with ethyl acetate.

Acetates↗
PubMed2005

The ins and outs of intracellular chloride in olfactory receptor neurons.

Stimulation of olfactory receptor neurons with odors culminates in opening of a ciliary Ca2+-activated Cl- channel. Because intracellular Cl- ([Cl-]i) is above electrochemical equilibrium in these cells, the result is cell depolarization that triggers action potentials that carry information to the olfactory bulb. In this issue of Neuron, Reisert and coworkers use combined pharmacological and mouse genetic approaches to show that the transporter responsible for maintaining Cl- above electrochemical equilibrium is NKCC1, a (Na+)(2Cl-)(K+) cotransporter found in other tissues, including neurons.

Animals↗
PubMed2005

Aberrant intracellular calcium signaling in olfactory neurons from patients with bipolar disorder.

OBJECTIVE: The authors examined the feasibility of using olfactory receptor neurons from living patients to test whether calcium signaling is altered in a neuronal cell population in bipolar disorder. METHOD: Ratiometric fluorescence photomicroscopy was used to assess basal and stimulus-induced changes in intracellular calcium levels in biopsy-derived olfactory receptor neurons from seven euthymic patients with bipolar disorder who were medication-free, 10 euthymic patients with bipolar disorder who were treated with mood stabilizers, and 17 age- and sex-matched comparison subjects without bipolar disorder. RESULTS: Olfactory receptor neurons from the seven medication-free patients responded to stimuli predominantly with decreases in intracellular calcium, unlike those from the seven matched healthy subjects. Olfactory receptor neurons from patients treated with mood stabilizers were less likely to respond to stimulation than olfactory receptor neurons from medication-free patients. CONCLUSIONS: This study demonstrates the feasibility of using olfactory receptor neurons to examine alterations in intracellular signaling in neuronal cells from living patients. Our results, although based on a small number of subjects, suggest that altered intracellular calcium signaling in olfactory receptor neurons may be a trait of bipolar disorder.

Anticonvulsants↗
PubMed2004

Odors detected by mice deficient in cyclic nucleotide-gated channel subunit A2 stimulate the main olfactory system.

It is believed that odor transduction in the mammalian main olfactory system only involves the cAMP-signaling pathway. Here, we report on odor responsiveness in mice with a disrupted cyclic nucleotide-gated (CNG) channel subunit A2. Several odorants, including putative pheromones, can be detected and discriminated by these mice behaviorally. These odors elicit responses in the olfactory epithelium, main olfactory bulb, and olfactory (piriform) cortex of CNGA2 knock-out mice. In addition, responses to odors detected by CNGA2 knock-out mice are relatively insensitive to inhibitors of the cAMP pathway. These results provide strong evidence that cAMP-independent pathways in the main olfactory system of mammals participate in detecting a subset of odors.

Animals↗
PubMed2004

Emerging views on the distinct but related roles of the main and accessory olfactory systems in responsiveness to chemosensory signals in mice.

In rodents, the nasal cavity contains two separate chemosensory epithelia, the main olfactory epithelium, located in the posterior dorsal aspect of the nasal cavity, and the vomeronasal/accessory olfactory epithelium, located in a capsule in the anterior aspect of the ventral floor of the nasal cavity. Both the main and accessory olfactory systems play a role in detection of biologically relevant odors. The accessory olfactory system has been implicated in response to pheromones, while the main olfactory system is thought to be a general molecular analyzer capable of detecting subtle differences in molecular structure of volatile odorants. However, the role of the two systems in detection of biologically relevant chemical signals appears to be partially overlapping. Thus, while it is clear that the accessory olfactory system is responsive to putative pheromones, the main olfactory system can also respond to some pheromones. Conversely, while the main olfactory system can mediate recognition of differences in genetic makeup by smell, the vomeronasal organ (VNO) also appears to participate in recognition of chemosensory differences between genetically distinct individuals. The most salient feature of our review of the literature is that there are no general rules that allow classification of the accessory olfactory system as a pheromone detector and the main olfactory system as a detector of general odorants. Instead, each behavior must be considered within a specific behavioral context to determine the role of these two chemosensory systems. In each case, one system or the other (or both) participates in a specific behavioral or hormonal response.

Animals↗
PubMed2004

Odorant responses of dual polarity are mediated by cAMP in mouse olfactory sensory neurons.

Some olfactory sensory neurons (OSNs) respond to odors with hyperpolarization. Although transduction for excitatory responses is mediated by opening of a cyclic nucleotide-gated (CNG) channel, there is controversy on the mechanism underlying inhibitory responses. We find that mouse OSNs respond to odorants by either depolarizing or hyperpolarizing responses in loose-patch measurements. In the perforated-patch configuration, OSNs not only responded with a current consistent with CNG channel-mediated excitation but also displayed enhancement of outward currents, consistent with inhibitory responses. Increasing cAMP levels pharmacologically elicited excitatory or inhibitory responses in different OSNs. In addition, OSNs from mice defective for the CNGA2 subunit of the CNG channel displayed neither excitatory nor inhibitory responses. Thus CNG channels mediate inhibitory olfactory responses.

Animals↗
PubMed2003

Heterogeneous expression of connexin 36 in the olfactory epithelium and glomerular layer of the olfactory bulb.

Gap junctions regulate a variety of cell functions by directly connecting two cells through intercellular channels. Connexins are gap junction channel-forming protein subunits. In this study, we studied the expression of connexin 36 (Cx36) in the olfactory epithelium and olfactory bulb of adult mice. In situ hybridization revealed that mRNA for Cx36 was expressed in the olfactory sensory epithelium, main olfactory bulb and accessory olfactory bulb. Expression of mRNA encoding Cx36 was observed in the olfactory epithelium mainly in ventral and lateral regions of the turbinates. Immunohistochemical determination of Cx36 protein expression showed sparse punctuate staining in the olfactory epithelial layer. Intense Cx36-like immunostaining was found in the olfactory nerve bundles underlying the olfactory epithelium and in the olfactory nerve layer and glomerular layer of the olfactory bulb. Mapping of the intensity of Cx36-like immunofluorescence in glomeruli throughout the main olfactory bulb indicated a heterogeneous distribution. A set of approximately 50 glomeruli located in the anterior and posterior limits of the olfactory bulb was more intensely labeled than other glomeruli. There was intense immunofluorescence signal in the glomerular layer of the accessory olfactory bulb and in the vomeronasal nerve. beta-Galactosidase distribution in the olfactory epithelium and olfactory bulb in Cx36 knockout mice (Deans et al. [2001] Neuron 31:477-485) supported the findings with immunofluorescence. Cx36-like immunofluorescence was absent in the olfactory nerve bundles in Cx36 knockout mice. The immunolocalization of Cx36 to the olfactory and vomeronasal nerves, and a subset of olfactory glomeruli suggest a functional role for Cx36 in odor coding.

Animals↗
PubMed2002

Olfactory fingerprints for major histocompatibility complex-determined body odors II: relationship among odor maps, genetics, odor composition, and behavior.

The olfactory system detects small differences in the composition of natural odorants, made up of hundreds of molecules. Odorous quality is hypothetically represented by a combinatorial code: activation of distinct but overlapping subsets of olfactory receptors resulting in activation of a distinct subset of glomeruli in the main olfactory bulb (MOB). Here we show that modification of a single gene (the K gene of the major histocompatibility locus), which results in a subtle change in the odiferous quality of urine, causes a small but significant change in the composition of urine volatiles and consequently the evoked glomerular activation pattern in the MOB. The magnitude of disparity between urine-evoked glomerular activation patterns is predictive of the extent of (1) the genetic difference among the urine donors, (2) the difference in the chemical composition of urine, and (3) the odor detector's ability to discriminate. These data on natural odors are consistent with the combinatorial code hypothesis and identify subsets of glomeruli that are apt to play a significant role in mediating individual recognition.

Animals↗
PubMed2002

Expression of connexin 45 in the olfactory system.

Gap junctions represent an important mode of intercellular communication. Connexin 45 (Cx45) is a member of the connexin family that forms gap junctions between adjacent cells. In this study, we demonstrate the expression of Cx45 in the olfactory epithelium and olfactory bulb in adult mice. Reverse transcription polymerase chain reaction amplification of total RNA from mouse turbinates and olfactory bulb yielded cDNA fragments partially encoding for Cx45. In situ hybridization using Cx45 cRNA probes revealed that hybridization products were more abundant in the olfactory epithelial layer than in the lamina propria underneath the epithelium. In the olfactory epithelial layer, hybridization signals were relatively intense in a band spreading from the basal cell layer to 4/5 of the distance from the basal cell layer to the apical process. The distribution of cells positive for Cx45 mRNA is largely overlapping with that of cells expressing olfactory marker protein mRNA, indicating that a substantial number of mature olfactory neurons express Cx45 mRNA. In the olfactory bulb, cells with large nuclei in the mitral cell layer, presumably mitral cells, express Cx45 mRNA. Immunoblotting with an antibody recognizing Cx45 revealed a band at approximately 46 kDa in homogenates of mouse turbinates and olfactory bulb. Immunohistochemical studies showed fine immunoreactive puncta in the olfactory epithelium. Immunoreactivity was observed surrounding cell bodies and the proximal processes of mitral cells in the olfactory bulb. The data suggest that Cx45 is a neuronal connexin that is expressed in mature neurons in adult mice. Our study implicates a functional role for Cx45 in the olfactory system deserving future study.

Animals↗