Faculty Bibliography

Background and aims: Dementia is considered a nonsupportive diagnostic feature for multiple system atrophy (MSA). Nevertheless, post-mortem verified dementia with Lewy bodies and Parkinson's disease masquerade as MSA. Cognitive impairment (CI), especially executive dysfunction, may occur in MSA patients. It is, however, unclear whether CI manifests in early disease stages.
Objective(s): To compare the prevalence of CI in MSA versus other Lewy Body disorders (LBD), including dementia with Lewy bodies and Parkinson's disease, in early (<3 years from symptom onset) versus more advanced disease stages (>=3 years from symptom onset).
Method(s): A total of 364 patients (LBD: n=83; MSA: n=281) of the natural history study of synucleinopathies register have been analysed. Consensus diagnostic criteria for dementia with Lewy bodies, Parkinson's disease and MSA were applied. To assess CI, the Montreal Cognitive Assessment (MoCA) has been used.
Result(s): In early disease stages, median MoCA scores did not differ significantly between MSA and LBD. In advanced disease stages, MSA patients had a significantly higher median MoCA score compared to LBD patients (27 versus 25, p=0.006). Comparison of the median MoCA Scores of LBD versus MSA patients at early and advanced disease stages
Conclusion(s): In patients with longer disease duration severity of CI helps to differentiate LBD from MSA

This review explores the relationship between vitamin D supplementation and lithogenesis. A causal relationship has been assumed despite myriad studies demonstrating that therapeutic doses of vitamin D do not increase lithogenic risk. Select stone formers may be at increased risk for recurrence with vitamin D supplementation, possibly from CYP24A1 gene mutations. Additionally, the evidence for who is vitamin D deficient, and the benefits of supplementation in those not at risk for rickets, is sparse. Concerns may be avoidable as vitamin D screening appears unnecessary in most patients, and superior pharmacology is available which increases bone density, while decreasing stone formation.

INTRODUCTION The mechanisms underlying B cell-mediated autoimmune disease and the origin of autoreactive B cells are not well understood. Human monoclonal autoantibodies (mAbs) are valuable tools for investigating both. In this study, we used mAbs derived from patients with the autoimmune disorder, myasthenia gravis (MG). A subset of patients with MG have pathogenic autoantibodies that recognize muscle specific tyrosine kinase (MuSK). The autoantibodies of MuSK MG are predominantly of the IgG4 subclass and functionally monovalent as a result of Fab-arm exchange. OBJECTIVE To gain insight into the origin and development of these unique autoantibodies. METHODS AND RESULTS We examined MG patient-derived mAbs, their corresponding germline-encoded unmutated common ancestors (UCA) and monovalent antigen-binding fragments (Fabs) to investigate how antigen-driven affinity maturation contributes to both binding and immunopathology. Mature mAbs, their UCA counterparts and mature monovalent Fabs bound to the MuSK autoantigen and retained their pathogenic capacity. However, monovalent UCA Fabs, which still bound the autoantigen, lost their pathogenic capacity. The mature Fabs were characterized by very high affinity (sub-nanomolar) driven by a rapid on-rate and slow off-rate. However, the UCA affinity was approximately 100-fold less than the mature Fabs, which was driven by a rapid off-rate. SUMMARY/CONCLUSION These findings indicate that the autoantigen initiates the autoimmune response in MuSK MG and drives autoimmunity through the accumulation of somatic hypermutations such that monovalent IgG4 Fab-arm exchanged MG autoantibodies reach a high affinity threshold required for pathogenic capacity

PURPOSE:To develop criteria to interpret mitochondrial transfer RNA (mt-tRNA) variants based on unique characteristics of mitochondrial genetics and conserved structural/functional properties of tRNA. METHODS:We developed rules on a set of established pathogenic/benign variants by examining heteroplasmy correlations with phenotype, tissue distribution, family members, and among unrelated families from published literature. We validated these deduced rules using our new cases and applied them to classify novel variants. RESULTS:Evaluation of previously reported pathogenic variants found that 80.6% had sufficient evidence to support phenotypic correlation with heteroplasmy levels among and within families. The remaining variants were downgraded due to the lack of similar evidence. Application of the verified criteria resulted in rescoring 80.8% of reported variants of uncertain significance (VUS) to benign and likely benign. Among 97 novel variants, none met pathogenic criteria. A large proportion of novel variants (84.5%) remained as VUS, while only 10.3% were likely pathogenic. Detection of these novel variants in additional individuals would facilitate their classification. CONCLUSION:Proper interpretation of mt-tRNA variants is crucial for accurate clinical diagnosis and genetic counseling. Correlations with tissue distribution, heteroplasmy levels, predicted perturbations to tRNA structure, and phenotypes provide important evidence for determining the clinical significance of mt-tRNA variants.

Background and aims: Distinguishing neurogenic orthostatic hypotension (nOH) from other causes of blood pressure (BP) instability is of pivotal importance in clinical practice. Norcliffe-Kaufmann et al. recently showed that when the ratio between the heart rate increase and the systolic BP fall after 3 minutes of passive head-up tilt (HUT) is <0.492, this indicates nOH. Here we aimed at validating this nOH ratio with standard arm-cuff BP measurements upon active standing (AS).
Method(s): We screened all patients who had undergone cardiovascular autonomic function testing at the Innsbruck Medical University between January 2008 and September 2019.
Result(s): We included 51 patients (27 with Parkinson's disease, 22 with multiple system atrophy) diagnosed with orthostatic hypotension either upon AS or HUT. 49 patients showed no BP overshoot after the Valsalva maneuver and were thus classified as having nOH. Out of these, 27 patients showed a systolic BP fall >=20mmHg in both the HUT and the AS and were considered for further analysis. The nOH ratio was <0.492 for 20 patients during HUT and for 19 patients during the AS. The sensitivity of the nOH ratio for neurogenic OH was therefore 74% upon HUT and 70% upon AS. The correlation between the nOH-ratio upon HUT and AS was strong (rho=0.86, p<0.001).
Conclusion(s): A nOH ratio <0.492 evaluated with standard arm-cuff heart rate and BP measurements has a good sensitivity for nOH both upon HUT and AS. This ratio can be therefore used as bedside nOH screening measure, if no tilt-test facilities are available

When similar visual stimuli are presented binocularly to both eyes, one perceives a fused single image. However, when the two stimuli are distinct, one does not perceive a single image; instead, one perceives binocular rivalry. That is, one perceives one of the stimulated patterns for a few seconds, then the other for few seconds, and so on - with random transitions between the two percepts. Most theoretical studies focus on rivalry, with few considering the coexistence of fusion and rivalry. Here we develop three distinct computational neuronal network models which capture binocular rivalry with realistic stochastic properties, fusion, and the hysteretic transition between. Each is a conductance-based point neuron model, which is multi-layer with two ocular dominance columns (L & R) and with an idealized "ring" architecture where the orientation preference of each neuron labels its location on a ring. In each model, the primary mechanism initiating binocular rivalry is cross-column inhibition, with firing rate adaptation governing the temporal properties of the transitions between percepts. Under stimulation by similar visual patterns, each of three models uses its own mechanism to overcome cross-column inhibition, and thus to prevent rivalry and allow the fusion of similar images: The first model uses cross-column feedforward inhibition from the opposite eye to "shut off" the cross-column feedback inhibition; the second model "turns on" a second layer of monocular neurons as a parallel pathway to the binocular neurons, rivaling out of phase with the first layer, and together these two pathways represent fusion; and the third model uses cross-column excitation to overcome the cross-column inhibition and enable fusion. Thus, each of the idealized ring models depends upon a different mechanism for fusion that might emerge as an underlying mechanism present in real visual cortex.

The combination of in vivo extracellular recording and genetic-engineering-assisted optical stimulation is a powerful tool for the study of neuronal circuits. Precise analysis of complex neural circuits requires high-density integration of multiple cellular-size light sources and recording electrodes. However, high-density integration inevitably introduces stimulation artifact. We present minimal-stimulation-artifact (miniSTAR) μLED optoelectrodes that enable effective elimination of stimulation artifact. A multi-metal-layer structure with a shielding layer effectively suppresses capacitive coupling of stimulation signals. A heavily boron-doped silicon substrate silences the photovoltaic effect induced from LED illumination. With transient stimulation pulse shaping, we reduced stimulation artifact on miniSTAR μLED optoelectrodes to below 50 μV_pp, much smaller than a typical spike detection threshold, at optical stimulation of >50 mW mm^-2 irradiance. We demonstrated high-temporal resolution (<1 ms) opto-electrophysiology without any artifact-induced signal quality degradation during in vivo experiments. MiniSTAR μLED optoelectrodes will facilitate functional mapping of local circuits and discoveries in the brain.

The majority of clinical trials targeting the tau protein in Alzheimer's disease and other tauopathies are tau immunotherapies. Because tau pathology correlates better with the degree of dementia than amyloid-β lesions, targeting tau is likely to be more effective in improving cognition than clearing amyloid-β in Alzheimer's disease. However, the development of tau therapies is in many ways more complex than for amyloid-β therapies as briefly outlined in this review. Most of the trials are on humanized antibodies, which may have very different properties than the original mouse antibodies. The impact of these differences are to a large extent unknown, can be difficult to decipher, and may not always be properly considered. Furthermore, the ideal antibody properties for efficacy are not well established and can depend on several factors. However, considering the varied approaches in clinical trials, there is a general optimism that at least some of these trials may provide functional benefits to patients suffering of various tauopathies.