Insights into the molecular triggers of parosmia based on gas chromatography olfactometry

Background Parosmia is a debilitating condition in which familiar smells become distorted and disgusting, with consequences for diet and mental health. It is a feature of post-infectious olfactory loss, particularly resulting from COVID-19. There is currently little understanding of its pathophysiology, and the prevailing hypothesis for the underlying mechanism is aberrant growth of regenerating olfactory sensory neurons after damage. Methods We use gas-chromatograph olfactometry to individually present components of a complex olfactory mixture as a rapid screening tool for assessment of both quantitative and qualitative olfactory dysfunction in those with and without parosmia. This allows them to report the associated sensory effects and to identify those molecules which are altered or parosmic in nature. Results Here we show 15 different molecular triggers of this symptom. These trigger molecules are common to many in the parosmic volunteer group and share certain characteristics such as extremely low olfactory threshold and common molecular structure Conclusions We posit that specific highly odour-active molecules are the cause of the parosmic symptom in most cases and initiate the sense of disgust, suggesting that parosmia is, at least in part, a receptor-level phenomenon

Enhanced axonal response of mitochondria to demyelination offers neuroprotection:implications for multiple sclerosis

Axonal loss is the key pathological substrate of neurological disability in demyelinating disorders, including multiple sclerosis (MS). However, the consequences of demyelination on neuronal and axonal biology are poorly understood. The abundance of mitochondria in demyelinated axons in MS raises the possibility that increased mitochondrial content serves as a compensatory response to demyelination. Here, we show that upon demyelination mitochondria move from the neuronal cell body to the demyelinated axon, increasing axonal mitochondrial content, which we term the axonal response of mitochondria to demyelination (ARMD). However, following demyelination axons degenerate before the homeostatic ARMD reaches its peak. Enhancement of ARMD, by targeting mitochondrial biogenesis and mitochondrial transport from the cell body to axon, protects acutely demyelinated axons from degeneration. To determine the relevance of ARMD to disease state, we examined MS autopsy tissue and found a positive correlation between mitochondrial content in demyelinated dorsal column axons and cytochromecoxidase (complex IV) deficiency in dorsal root ganglia (DRG) neuronal cell bodies. We experimentally demyelinated DRG neuron-specific complex IV deficient mice, as established disease models do not recapitulate complex IV deficiency in neurons,and found that these mice are able to demonstrate ARMD, despite the mitochondrial perturbation.Enhancement of mitochondrial dynamics in complex IV deficient neurons protects the axon upon demyelination. Consequently, increased mobilisation of mitochondria from the neuronal cell body to the axon is a novel neuroprotective strategy for the vulnerable, acutely demyelinated axon. We propose that promoting ARMD is likely to be a crucial preceding step for implementing potential regenerative strategies for demyelinating disorders.</p

Enhanced axonal response of mitochondria to demyelination offers neuroprotection:implications for multiple sclerosis

Axonal loss is the key pathological substrate of neurological disability in demyelinating disorders, including multiple sclerosis (MS). However, the consequences of demyelination on neuronal and axonal biology are poorly understood. The abundance of mitochondria in demyelinated axons in MS raises the possibility that increased mitochondrial content serves as a compensatory response to demyelination. Here, we show that upon demyelination mitochondria move from the neuronal cell body to the demyelinated axon, increasing axonal mitochondrial content, which we term the axonal response of mitochondria to demyelination (ARMD). However, following demyelination axons degenerate before the homeostatic ARMD reaches its peak. Enhancement of ARMD, by targeting mitochondrial biogenesis and mitochondrial transport from the cell body to axon, protects acutely demyelinated axons from degeneration. To determine the relevance of ARMD to disease state, we examined MS autopsy tissue and found a positive correlation between mitochondrial content in demyelinated dorsal column axons and cytochrome c oxidase (complex IV) deficiency in dorsal root ganglia (DRG) neuronal cell bodies. We experimentally demyelinated DRG neuron-specific complex IV deficient mice, as established disease models do not recapitulate complex IV deficiency in neurons, and found that these mice are able to demonstrate ARMD, despite the mitochondrial perturbation. Enhancement of mitochondrial dynamics in complex IV deficient neurons protects the axon upon demyelination. Consequently, increased mobilisation of mitochondria from the neuronal cell body to the axon is a novel neuroprotective strategy for the vulnerable, acutely demyelinated axon. We propose that promoting ARMD is likely to be a crucial preceding step for implementing potential regenerative strategies for demyelinating disorders.</p

Finishing the euchromatic sequence of the human genome

The sequence of the human genome encodes the genetic instructions for human physiology, as well as rich information about human evolution. In 2001, the International Human Genome Sequencing Consortium reported a draft sequence of the euchromatic portion of the human genome. Since then, the international collaboration has worked to convert this draft into a genome sequence with high accuracy and nearly complete coverage. Here, we report the result of this finishing process. The current genome sequence (Build 35) contains 2.85 billion nucleotides interrupted by only 341 gaps. It covers ∼99% of the euchromatic genome and is accurate to an error rate of ∼1 event per 100,000 bases. Many of the remaining euchromatic gaps are associated with segmental duplications and will require focused work with new methods. The near-complete sequence, the first for a vertebrate, greatly improves the precision of biological analyses of the human genome including studies of gene number, birth and death. Notably, the human enome seems to encode only 20,000-25,000 protein-coding genes. The genome sequence reported here should serve as a firm foundation for biomedical research in the decades ahead

Chronic rhinosinusitis with and without nasal polyps and asthma: Omalizumab improves residual anxiety but not depression

Abstract Background Chronic rhinosinusitis (CRS) has a high prevalence of anxiety and depression. It is currently uncertain if treatment in patients with CRS with or without nasal polyps (CRSwNP and CRSsNP) has any impact on improving mental health outcomes. The aims here were to document anxiety and depression in patients with severe CRS and asthma already treated with appropriate medical therapy. We then evaluated whether further maximal treatment with omalizumab improved anxiety and/or depression alongside improvements in CRS and coassociated asthma. Methods Hospital Anxiety and Depression Scale (HADS) scores along with measures of CRS and asthma severity were recorded according to CRSwNP and CRSsNP status in n = 95 patients with severe CRS and asthma. Of this group, a further n = 23 had omalizumab for associated allergic asthma. Follow‐up measures were collected 16 weeks after omalizumab treatment. Results HADS anxiety and depression prevalence in CRS were 49.47 % and 38.95%, respectively. Within the CRSwNP and CRSsNP group 53.06% and 45.66% had raised HADS‐anxiety scores. Abnormal HADS‐depression scores were present in 40.82% and 36.95% of the CRSwNP and CRSsNP groups, respectively. Correlations for sinonasal outcome test‐22 (SNOT‐22) versus HADS total was r = 0.59 p < 0.0001, HADS‐anxiety r = 0.56 p < 0.0001 and HADS‐depression r = 0.49 p < 0.0001. Omalizumab improved anxiety in CRS (p < 0.0001) regardless of nasal polyp status (CRSwNP p = 0.0042 and CRSsNP p = 0.0078). Depression scores did not improve in either group. SNOT‐22 (p = 0.0006), asthma control questionnaire‐7 (p = 0.0019) and mini‐asthma quality of life questionnaire including emotional function (p = 0.0003 and p = 0.0009, respectively) all improved in both subgroups. Conclusion In CRS and asthma, anxiety scores but not depression improved after omalizumab treatment. Anxiety may be closely related to airway disease severity, but depression may be independent of airway disease itself. If so, a separate mental health care pathway is needed for CRS patients with depression