Olfactory Deficiency Research Articles

A Comprehensive Review of COVID-19-Related Olfactory Deficiency: Unraveling Associations with Neurocognitive Disorders and Magnetic Resonance Imaging Findings.

Olfactory dysfunction (OD) is one of the most common symptoms in COVID-19 patients and can impact patients' lives significantly. The aim of this review was to investigate the multifaceted impact of COVID-19 on the olfactory system and to provide an overview of magnetic resonance (MRI) findings and neurocognitive disorders in patients with COVID-19-related OD. Extensive searches were conducted across PubMed, Scopus, and Google Scholar until 5 December 2023. The included articles were 12 observational studies and 1 case report that assess structural changes in olfactory structures, highlighted through MRI, and 10 studies correlating the loss of smell with neurocognitive disorders or mood disorders in COVID-19 patients. MRI findings consistently indicate volumetric abnormalities, altered signal intensity of olfactory bulbs (OBs), and anomalies in the olfactory cortex among COVID-19 patients with persistent OD. The correlation between OD and neurocognitive deficits reveals associations with cognitive impairment, memory deficits, and persistent depressive symptoms. Treatment approaches, including olfactory training and pharmacological interventions, are discussed, emphasizing the need for sustained therapeutic interventions. This review points out several limitations in the current literature while exploring the intricate effects of COVID-19 on OD and its connection to cognitive deficits and mood disorders. The lack of objective olfactory measurements in some studies and potential validity issues in self-reports emphasize the need for cautious interpretation. Our research highlights the critical need for extensive studies with larger samples, proper controls, and objective measurements to deepen our understanding of COVID-19's long-term effects on neurological and olfactory dysfunctions.

Peripheric and central smell regions in patients with chronic rhinosinusitis with nasal polyps: An MRI evaluation

Abstract OBJECTIVE. We evaluated the effect of olfactory deficiency caused by sinonasal polyposis using a magnetic resonance imaging (MRI) evaluation. MATERIAL AND METHODS. In this retrospective study, 33 adult patients with bilateral chronic rhinosinusitis with nasal polyps (CRSwNP) (Group 1) and 30 healthy subjects without nasal polyps (Control, Group 2) were included. On coronal T2 weighted SPIR images of the MRI, the olfactory bulb (OB) volume and the olfactory sulcus (OS) depth were measured; the same action was performed on the axial T1 weighted images, for the corpus amygdala and insular gyrus areas. RESULTS. OB volume, insular gyrus and corpus amygdala areas of the CRSwNP group were significantly lower than those in the control group (p<0.05). In the CRSwNP group, there were positive correlations between OB volumes, OS depths, and insular gyrus areas and corpus amygdala areas bilaterally (p<0.05). In females, bilateral insular gyrus areas decreased compared to the males (p<0.05). When polyp duration got longer, the right corpus amygdala area decreased (p<0.05). In older patients with a CRSwNP, the left corpus amygdala area decreased (p<0.05). CONCLUSION. OB volume was found to be smaller in the CRSwNP group. We think that the OB volume has decreased primarily due to decreased transfer of odor particles (sensory input) related to nasal obstruction and inflammation in the presence of nasal polyps. After OB volume shrinkage, the insular gyrus and corpus amygdala areas shrink due to the decreased data transfer to the central odor system. In patients with nasal polyps, olfactory functions may improve after endoscopic sinus surgery.

Elevated Expression of RGS2 May Underlie Reduced Olfaction in COVID-19 Patients.

Anosmia is common in COVID-19 patients, lasting for weeks or months following recovery. The biological mechanism underlying olfactory deficiency in COVID-19 does not involve direct damage to nasal olfactory neurons, which do not express the proteins required for SARS-CoV-2 infection. A recent study suggested that anosmia results from downregulation of olfactory receptors. We hypothesized that anosmia in COVID-19 may also reflect SARS-CoV-2 infection-driven elevated expression of regulator of G protein signaling 2 (RGS2), a key regulator of odorant receptors, thereby silencing their signaling. To test our hypothesis, we analyzed gene expression of nasopharyngeal swabs from SARS-CoV-2 positive patients and non-infected controls (two published RNA-sequencing datasets, 580 individuals). Our analysis found upregulated RGS2 expression in SARS-CoV-2 positive patients (FC = 14.5, Padj = 1.69 × 10−5 and FC = 2.4; Padj = 0.001, per dataset). Additionally, RGS2 expression was strongly correlated with PTGS2, IL1B, CXCL8, NAMPT and other inflammation markers with substantial upregulation in early infection. These observations suggest that upregulated expression of RGS2 may underlie anosmia in COVID-19 patients. As a regulator of numerous G-protein coupled receptors, RGS2 may drive further neurological symptoms of COVID-19. Studies are required for clarifying the cellular mechanisms by which SARS-CoV-2 infection drives the upregulation of RGS2 and other genes implicated in inflammation. Insights on these pathway(s) may assist in understanding anosmia and additional neurological symptoms reported in COVID-19 patients.

Aggregation pheromone 4-vinylanisole promotes the synchrony of sexual maturation in female locusts.

Reproductive synchrony generally occurs in various group-living animals. However, the underlying mechanisms remain largely unexplored. The migratory locust, Locusta migratoria, a worldwide agricultural pest species, displays synchronous maturation and oviposition when forms huge swarm. The reproductive synchrony among group members is critical for the maintenance of locust swarms and population density of next generation. Here, we showed that gregarious female locusts displayed more synchronous sexual maturation and oviposition than solitarious females and olfactory deficiency mutants. Only the presence of gregarious male adults can stimulate sexual maturation synchrony of female adults. Of the volatiles emitted abundantly by gregarious male adults, the aggregation pheromone, 4-vinylanisole, was identified to play key role in inducing female sexual maturation synchrony. This maturation-accelerating effect of 4-vinylanisole disappeared in the females of Or35-/- lines, the mutants of 4-vinylanisole receptor. Interestingly, 4-vinylanisole displayed a time window action by which mainly accelerates oocyte maturation of young females aged at middle developmental stages (3-4 days post adult eclosion). We further revealed that juvenile hormone/vitellogenin pathway mediated female sexual maturation triggered by 4-vinylanisole. Our results highlight a 'catch-up' strategy by which gregarious females synchronize their oocyte maturation and oviposition by time-dependent endocrinal response to 4-vinylanisole, and provide insight into reproductive synchrony induced by olfactory signal released by heterosexual conspecifics in a given group.

CRISPR-mediated mutagenesis of the odorant receptor co-receptor (Orco) gene disrupts olfaction-mediated behaviors in Bactrocera dorsalis.

Olfaction plays an essential role in insect behavior such as host location, foraging, mating, and oviposition. The odorant receptor co-receptor (Orco) is an obligatory odorant receptor and indispensable in odor perception. Here, we characterized the Orco gene from the oriental fruit fly, Bactrocera dorsalis (Hendel), a notorious agriculture pest. The olfactory deficiency mutants were generated by editing the BdorOrco gene using the CRISPR/Cas9 system. Electroantennograms (EAG) and olfactory preference assays confirmed that BdorOrco-/- mutant flies had reduced perception of methyl eugenol, β-caryophyllene, and ethyl acetate. Oviposition bioassays showed that the eggs laid by BdorOrco-/- females mediated by benzothiazole and 1-octen-3-ol were significantly decreased. In addition, BdorOrco-/- mutant flies took a significantly longer time to locate the food source compared with wild type (WT) flies. Altogether, our data indicated that Orco is essential for multiple physiological processes in B. dorsalis, and it expands our understanding of the function of insect Orco.

Lipidomic profile of human nasal mucosa and associations with circulating fatty acids and olfactory deficiency

The nasal mucosa (NM) contains olfactory mucosa which contributes to the detection of odorant molecules and the transmission of olfactory information to the brain. To date, the lipid composition of the human NM has not been adequately characterized. Using gas chromatography, liquid chromatography coupled to mass spectrometry and thin layer chromatography, we analyzed the fatty acids and the phospholipid and ceramide molecular species in adult human nasal and blood biopsies. Saturated and polyunsaturated fatty acids (PUFAs) accounted for 45% and 29% of the nasal total fatty acids, respectively. Fatty acids of the n-6 family were predominant in the PUFA subgroup. Linoleic acid and arachidonic acid (AA) were incorporated in the main nasal phospholipid classes. Correlation analysis revealed that the nasal AA level might be positively associated with olfactory deficiency. In addition, a strong positive association between the AA levels in the NM and in plasma cholesteryl esters suggested that this blood fraction might be used as an indicator of the nasal AA level. The most abundant species of ceramides and their glycosylated derivatives detected in NM contained palmitic acid and long-chain fatty acids. Overall, this study provides new insight into lipid species that potentially contribute to the maintenance of NM homeostasis and demonstrates that circulating biomarkers might be used to predict nasal fatty acid content.

Reversible olfactory dysfunction impaired learning and memory with impaired hippocampal synaptic plasticity and increased corticosterone release in mice

Olfactory dysfunction is related with various neurodegenerative and neuropsychiatric disorders such as Alzheimer's disease and Parkinson's disease, which show impaired cognitive functions. However, the effects of olfactory dysfunction on hippocampal dependent learning and memory remain elusive. In this study, mice were treated with intranasal zinc sulfate (ZnSO4) infusion which resulted in a complete but reversible loss of olfactory function. Olfaction was totally destroyed even 1 week after zinc sulfate treatment, but partially recovered 4 weeks later. We found learning and memory in Y-maze and fear conditioning were not affected by ZnSO4 1 week after the treatment, but learning and memory were severely destroyed 4 weeks later. Electrophysiology results showed impaired hippocampal long-term potentiation and long-term depression 4 weeks after the olfaction dysfunction, while only long-term depression was impaired 1 week after the treatment. Western blot showed that the expression and phosphorylation of GluA1 in zinc group did not show any increase after fear conditioning as the control mice. Serum corticosterone release was increased in olfactory deficit mice at baseline and after acute stress when tested 3, 10 and 20 days after the olfactory dysfunction. All these results indicated that reversible olfactory dysfunction elicited impaired hippocampal function in mice. The higher corticosterone release after olfactory deficiency might serve as an underling mechanism.

Intranasal administration of white tea alleviates the olfactory function deficit induced by chronic unpredictable mild stress

Context White tea [Camellia sinensis (L) O.Ktze. (Theaceae)] is popular in Asia, but its benefits on olfactory injury are unknown. Objective The present study explores the effects of white tea on the olfactory injury caused by chronic unpredictable mild stress (CUMS). Materials and methods C57BL/6J mice (WT) were exposed to CUMS. CUMS mice (CU) were intranasally treated with white tea extract [low tea (LT), 20 mg/kg; high tea (HT), 40 mg/kg] and fluoxetine (CF, 20 mg/kg) for 7 days. Several behavioural tests were conducted to assess depression and olfactory function. The transmission electron microscope (TEM) and semi-quantitative reverse transcription PCR were performed separately to observe the changes of related structures and genes transcription level. Results The depressive behaviours of the LT and HT mice were reversed. The latency time of the buried food pellet test decreased from 280 s (CU) to 130 s (HT), while the olfactory sensitivity and olfactory avoidance test showed that the olfactory behaviours disorder of LT and HT mice were alleviated. The white tea increased the A490 nm values of the cortisol treated cells from 0.15 to 1.4. Reduced mitochondrial and synaptic damage in the olfactory bulb (OB), enhanced expression of the brain-derived neurotrophic factor (BDNF) and olfactory marker protein (OMP) were observed in the LT and HT mice. Conclusions and discussion White tea has the potential in curing the olfactory deficiency related to chronic stress. It lays the foundation for the development of new and reliable drug to improve olfactory.

In Vivo Inspection of the Olfactory Epithelium: Feasibility of Robotized Optical Biopsy.

Inspecting the olfactory cleft can be of high interest, as it is an open access to neurons, and thus an opportunity to collect in situ related data in a non-invasive way. Also, recent studies show a strong link between olfactory deficiency and neurodegenerative diseases such as Alzheimer and Parkinson diseases. However, no inspection of this area is possible today, as it is very difficult to access. Only robot-assisted interventions seem viable to provide the required dexterity. The feasibility of this approach is demonstrated in this article, which shows that the path complexity to the olfactory cleft can be managed with a concentric tube robot (CTR), a particular type of continuum robot. First, new anatomical data are elaborated, in particular for the olfactory cleft, that remains hardly characterized. 3D reconstructions are conducted on the database of 20 subjects, using CT scan images. Measurements are performed to describe the anatomy, including metrics with inter-subject variability. Then, the existence of collision-free passageways for CTR is shown using the 3D reconstructions. Among the 20 subjects, 19 can be inspected using only 3 different robot geometries. This constitutes an essential step towards a robotic device to inspect subjects for clinical purposes.

Olfactory cues play a significant role in removing fungus from the body surface of Drosophila melanogaster.

Many insects and Dipterans in particular are known to spend considerable time grooming, but whether these behaviors actually are able to remove pathogenic fungal conidia is less clear. In this study, we examined whether grooming serves to protect flies by reducing the risk of fungal infection in Drosophila melanogaster. First, we confirmed that fungi were removed by grooming. Entomopathogenic, opportunistic, and plant pathogenic fungi were applied on the body surface of the flies. To estimate grooming efficiency, the number of removal conidia through grooming was quantified and we successfully demonstrated that flies remove fungal conidia from their body surfaces via grooming behavior. Second, the roles of gustatory and olfactory signals in fungus removal were examined. The wildtype fly Canton-S, the taste deficiency mutant poxn 70, and the olfactory deficiency mutant orco1 were used in the tests. Comparisons between Canton-S and poxn 70 flies indicated that gustatory signals do not have a significant role in fungal removal via grooming behavior in D. melanogaster. In contrast, the efficiency of conidia removal in orco1 flies was drastically decreased. Consequently, this study indicated that flies rely on mechanical stimulus for the induction of grooming and olfaction for more detailed removal.

CRISPR/Cas9 in locusts: Successful establishment of an olfactory deficiency line by targeting the mutagenesis of an odorant receptor co-receptor (Orco)

Locusts are important agricultural pests worldwide and regarded as study models for entomology. However, the absence of targeted gene manipulation systems for locusts has restricted their applications for research. Herein, we report the successful use of the CRISPR/Cas9 system to induce a targeted heritable mutagenesis of the migratory locust, Locusta migratoria. The target sequence of gRNA was designed to disrupt the gene encoding the odorant receptor co-receptor (Orco) and examine the roles of the odorant receptor pathway in the locust. Microinjection of the mixture of Cas9-mRNA and Orco-gRNA into the locust eggs resulted in efficient target-gene editing at a rate of 71.7% in G0 animals and achieved a germline efficiency of up to 88.1% in G1 animals. By a crossing strategy, we successfully established stable Orco mutant lines. EAGs and SSRs indicated that the fourth-instar nymphs of the Orco mutants showed severely impaired electrophysiological responses to multiple odors. The Orco mutant locusts lost an attraction response to aggregation pheromones under the crowding conditions. The locomotor activity and body coloration of the Orco mutant locusts did not significantly differ from those of the two other genotypes. This study provides an easy and effective approach by using the CRISPR/Cas9 system for generating loss-of-function mutants for functional genetic studies of locusts and for managing insect pests.

Anxiety- and depressive-like behaviors in olfactory deficient Cnga2 knockout mice

There is a close neuroanatomical connection between odor and emotional processing. Olfactory dysfunction is found in various neurodegenerative and neuropsychiatric disorders. Here, mice take the cyclic nucleotide gated channel 2 mutant gene (Cnga2), which is critical for olfactory sensory neurons to generate odor induced action potentials were used. The Cnga2 mice were congenitally anosmic. Adult mice were tested in a series behavioral paradigm such as open field, light/dark box, forced swim test and Y-maze. Our study found that Cnga2 mice showed increased anxiety- and depressive-like behaviors than their wide type siblings. However, Cnga2 mice showed no difference from the wide types when tested in the two-trial recognition Y-maze. The results indicate that innate olfactory deficiency might modulate emotional behaviors in mice.

Effects of maternal immune activation on adult neurogenesis in the subventricular zone–olfactory bulb pathway and olfactory discrimination

Maternal infection and maternal immune activation (MIA) during pregnancy increase risks for psychiatric disorders such as schizophrenia and autism. Many deficits related to psychiatric disorders are observed in adult offspring of MIA animal models, including behavioral abnormalities, morphological defects in various brain regions, and dysregulation of neurotransmitter systems. It has previously been shown that MIA impairs adult neurogenesis in the dentate gyrus of the hippocampus. In this study, we examined whether MIA affects adult neurogenesis in the subventricular zone (SVZ)–olfactory bulb (OB) pathway. Polyinosinic–polycytidylic acid (PolyI:C), a synthetic analog of double-stranded RNA mimicking viral infection, was injected into pregnant mice on gestation day 9.5 to activate immune systems. In the SVZ–OB pathway of adult offspring, different cell types of the neural stem cell lineage responded differently to MIA. Neural stem cells and neuroblasts were decreased. Cell proliferation of transit-amplifying cells was impaired. Consequently, newborn neurons were reduced in the OB. Olfactory deficiency has been suggested as a biomarker for schizophrenia. Here we found that olfactory discrimination was compromised in adult MIA offspring. Taken together, these findings show that MIA leads to defective adult neurogenesis in the SVZ–OB pathway, and the impairment of adult neurogenesis may lead to deficits in olfactory functions.

Reduced olfactory bulb volume and diminished olfactory function in total laryngectomy patients: A prospective longitudinal study

This study was designed to investigate the effects of total laryngectomy on olfactory bulb (OB) volume and olfactory function prospectively. A prospective, longitudinal, randomized study was performed. Fifteen subjects with advanced cancer of the larynx were recruited. The OB volume was measured preoperatively and 6 months postoperatively using magnetic resonance imaging (MRI) and olfactory function was assessed using the Connecticut Chemosensory Clinical Research Center (CCCRC) test. A detailed otorhinolaryngological examination was conducted and abnormalities that could potentially cause olfactory dysfunction were excluded. An experienced radiologist segmented the MRI coronal slices manually for OB volume measurements. The difference between the right and left OB volumes was not significant. OB volume decreased significantly 6 months postoperatively, from 64.2 to 47.1 mm(3) (p < 0.001). The CCCRC test results, scored out of 8, decreased significantly from 5.6 to 2.4 (p < 0.001) and all patients were either anosmic or hyposmic. This longitudinal prospective study was the first to examine the cessation of olfactory stimulation in olfactory deficiency resulting from OB functional and structural changes.

Neuroligin‐3‐deficient mice: model of a monogenic heritable form of autism with an olfactory deficit

Autism spectrum disorder (ASD) is a frequent neurodevelopmental disorder characterized by variable clinical severity. Core symptoms are qualitatively impaired communication and social behavior, highly restricted interests and repetitive behaviors. Although recent work on genetic mutations in ASD has shed light on the pathophysiology of the disease, classifying it essentially as a synaptopathy, no treatments are available to date. To develop and test novel ASD treatment approaches, validated and informative animal models are required. Of particular interest, in this context are loss-of-function mutations in the postsynaptic cell adhesion protein neuroligin-4 and point mutations in its homologue neuroligin-3 (NL-3) that were found to cause certain forms of monogenic heritable ASD in humans. Here, we show that NL-3-deficient mice display a behavioral phenotype reminiscent of the lead symptoms of ASD: reduced ultrasound vocalization and a lack of social novelty preference. The latter may be related to an olfactory deficiency observed in the NL-3 mutants. Interestingly, such olfactory phenotype is also present in a subgroup of human ASD patients. Tests for learning and memory showed no gross abnormalities in NL-3 mutants. Also, no alterations were found in time spent in social interaction, prepulse inhibition, seizure propensity and sucrose preference. As often seen in adult ASD patients, total brain volume of NL-3 mutant mice was slightly reduced as assessed by magnetic resonance imaging (MRI). Our findings show that the NL-3 knockout mouse represents a useful animal model for understanding pathophysiological events in monogenic heritable ASD and for developing novel treatment strategies in this devastating human disorder.

Early locus coeruleus degeneration and olfactory dysfunctions in Tg2576 mice

Olfactory deficiency has been reported in the early stages of Alzheimer's disease (AD) in humans but is very poorly understood due to the lack of investigations in animal models of AD. Recent studies point to the noradrenergic system as an important target of the AD pathological process. In addition, noradrenalin has been shown to influence adult neurogenesis which is implicated in cognitive functions. We have therefore investigated the olfactory neurogenesis and cognitive performances in young transgenic Tg2576 mice in relation with the status of the noradrenergic and the cholinergic systems. Tg2576 showed a deficit in neurogenesis in the olfactory bulb evidenced by an increased death of newborn cells and a reduced expression of PSA-NCAM. The locus coeruleus degenerated in Tg2576 between the age of 6.5 and 8 months. These changes were associated with olfactory memory impairments. Our findings indicate that a noradrenergic deficiency could play a role in the early stages of the pathological process in this transgenic model and induce olfactory cognitive impairments through an alteration of olfactory neurogenesis.

Clinical Significance of Results from Olfactory Testing

Although widely used in healthy subjects and patients with olfactory loss, the significance of changes of scores from validated olfactory tests is unknown. The aim of the present study was to relate the self-assigned changes of olfactory function in terms of "better," "unchanged," and "worse" in patients with smell disorders with the results from olfactory testing by means of a validated test set. Olfactory function of 83 anosmic or hyposmic patients (40 women, 43 men; age 12-84 yr) was tested on two occasions (mean interval 136 days, minimum 7 days, maximum 6.7 yr). Olfactory function was assessed using a validated technique ("Sniffin' Sticks"). This test consists of three subtests, one for odor threshold (T), odor discrimination (D), and odor identification (I), with possible results ranging up to 16 points each. From the sum of the results from the three subtests a composite "TDI" score was obtained. Forty-four patients indicated an improvement of olfactory function, whereas 39 patients reported no change. No subject reported deterioration of olfactory sensitivity. Subjects assigned to group BETTER had higher TDI scores in the second olfactory tests than subjects assigned to the group UNCHANGED, both in absolute terms and as compared with the first olfactory test (effect "test occasion" by "self-assessed improvement," P < .001). There was no significant difference between groups with respect to age and sex (P = .99 and .84, respectively). Logistic regression showed that more than 60% of the subjects reported an improvement of olfactory sensitivity when the TDI score increased by 5.5 points. We show that there is a statistically significant relation between measured and perceived improvement of olfactory function in patients who first presented with the diagnosis of anosmia or hyposmia. The results indicate that improved olfactory function in patients with olfactory deficiency is perceived as such in everyday life and is quantitatively related to an improvement in the composite TDI score of the "Sniffin' Sticks" olfactory test battery. This is the basis for the application of a specific therapy for olfactory loss because of a possible gain in quality of life for the patients.

Olfactory Evaluation in Children: Application to the CHARGE Syndrome

To find an efficient tool for testing olfactory function in children and use it to investigate a group of children with CHARGE (coloboma, congenital heart disease, choanal atresia, mental and growth retardation, genital anomalies, and ear malformations and hearing loss) syndrome. We adapted for children an olfaction test that had just been validated in an adult French population and investigated a control group of 25 healthy children aged 6 to 13 years. We then tested the olfactory capacity of a group of 14 children with CHARGE syndrome, aged 6 to 18 years. A questionnaire was completed with the parents about their children's feeding difficulties and their ability to recognize odors in everyday life. We recorded and scored the histories of feeding behavior anomalies, the visual and auditory status, and current intellectual levels. MRI of the olfactory tracts and bulbs was analyzed for 9 of 14 children. We showed that healthy children have similar olfactory function to that of the adult control group, which was representative of the general population, without any difference for either gender or age. We also showed that all children with CHARGE syndrome had olfactory deficiency. Half of them were anosmic, and the others had olfactory residual function (hyposmic). We found no association between olfactory deficiency and feeding behavior, visual or auditory impairment, or intellectual level. Parental subjective evaluations were accurate for only half of the group. All of the MRIs showed anomalies of the olfactory tracts and bulbs varying from moderate hypoplasia to complete aplasia, without any relation between the radiologic and the functional results. Olfaction can be assessed in children, even the young and disabled. Our results support the proposition that rhinencephalon anomalies should be included as a major criterion for the diagnosis of CHARGE syndrome.

カルマン症候群におけるきゅう裂部の電子顕微鏡的観察

A 52-year-old man with Kallmann syndrome (olfacto-genital dysplasia) had abnormally low serum gonadotropic hormone and testosterone levels. The LH-RH test revealed little response.Small pieces of mucosa were experimentally resected from the olfactory area of both sides of the nasal cavity and examined morphologically with scanning and transmission electron microscopes. Ciliated cells, mucus secreting (goblet) cells, and basal cells, which are characteristic epithelial cells of the respiratory system, were densely distributed, but no olfactory epithelial cells or their neural processes were seen. In this case, these observations indicate a complete olfactory deficiency caused by agenesis of at least the peripheral portion of the neural olfactory system. Further investigations are necessary to determine the relationship between the pathology and the degree of olfactory disturbance in Kallmann syndrome.

Hypoglycemia induced by olfactory denervation in turtle (Chrysemys d'orbigni)

Adult male turtles Chyrsemys d'orbigni with olfactory deficiency caused by olfactory deafferentation or by olfactory bulbectomy were used. Four, six and eight months later the lesioned turtles showed significantly lower blood glucose level than control animals. The hypoglycemia was similar in bulbectomized and deafferented turtles.