How Zebrafish Can Drive the Future of Genetic-based Hearing and Balance Research

Over the last several decades, studies in humans and animal models have successfully identified numerous molecules required for hearing and balance. Many of these studies relied on unbiased forward genetic screens based on behavior or morphology to identify these molecules. Alongside forward genetic screens, reverse genetics has further driven the exploration of candidate molecules. This review provides an overview of the genetic studies that have established zebrafish as a genetic model for hearing and balance research. Further, we discuss how the unique advantages of zebrafish can be leveraged in future genetic studies. We explore strategies to design novel forward genetic screens based on morphological alterations using transgenic lines or behavioral changes following mechanical or acoustic damage. We also outline how recent advances in CRISPR-Cas9 can be applied to perform reverse genetic screens to validate large sequencing datasets. Overall, this review describes how future genetic studies in zebrafish can continue to advance our understanding of inherited and acquired hearing and balance disorders.     

Individuals with peripheral vestibulopathy and poor quality of sleep are at a higher risk for falls

IntroductionThere is a lack of scientific studies on the assessment of patients with vestibular disorders associated with sleep quality disorders and its impact on the balance and overall quality of life.Objectivesto assess the impact of the sleep quality on the balance and quality of life of individuals with peripheral vestibulopathies.Methods52 individuals with peripheral vestibulopathies underwent sleep quality assessment through the Pittsburgh sleep quality index, neurotological examination through dizziness handicap inventory and Tetrax posturography (Sunlight Medical Ltd.) in eight sensory conditions. Thirty-two healthy individuals (G3) participated as the control group.ResultsFourteen individuals with vestibulopathy had good quality of sleep (G1) and 38 showed poor quality of sleep (G2) as demonstrated by the Pittsburgh sleep quality index global scores (p = 0.001). The dizziness handicap inventory showed worse impact of the dizziness on the quality of life in G2 when compared to G1 (p  = 0.045). The G₂ showed higher risk of falling in posturography when compared to G3 (p = 0.012) and higher index of postural instability in five sensory conditions in comparison with G3. In the vestibulopathy groups, the worse the sleep quality, the higher the risk of falling (r = 0.352) and the worse the quality of life (r = 0.327).ConclusionIndividuals with peripheral vestibulopathies and poor quality of sleep demonstrate worse balance evidenced by increased postural instability, higher risk of falls and worse perceived quality of life. The quality of sleep is a predictive factor for worse perceived quality of life and for higher risk of falls in individuals with peripheral vestibulopathies.     

Permeation of Fluorophore-Conjugated Phalloidin into Live Hair Cells of the Inner Ear Is Modulated by P2Y Receptors

Phalloidin, a toxin isolated from the death cap mushroom, Amanita phalloides, binds to filamentous actin with high affinity, and this has made fluorophore-conjugated phalloidin a useful tool in cellular imaging. Hepatocytes take up phalloidin via the liver-specific organic anion transporting polypeptide 1b2, but phalloidin does not permeate most living cells. Rapid entry of styryl dyes into live hair cells has been used to evaluate function, but the usefulness of those fluorescence dyes is limited by broad and fixed absorption spectra. Since phalloidin can be conjugated to fluorophores with various spectra, we investigated whether it would permeate living hair cells. When we incubated mouse utricles in 66 nM phalloidin-CF488A and followed that by washes in phalloidin-free medium, we observed that it entered a subset of hair cells and labeled entire hair bundles fluorescently after 20 min. Incubations of 90 min labeled nearly all the hair bundles. When phalloidin-treated utricles were cultured for 24 h after washout, the label disappeared from the hair cells and progressively but heterogeneously labeled filamentous actin in the supporting cells. We investigated how phalloidin may enter hair cells and found that P2 receptor antagonists, pyridoxalphosphate-6-azophenyl-2′, 4′-disulfonic acid and suramin, blocked phalloidin entry, while the P2Y receptor ligands, uridine-5’-diphosphate and uridine-5’-triphosphaste, stimulated uptake. Consistent with that, the P2Y6 receptor antagonist, MRS 2578, decreased phalloidin uptake. The results show that phalloidin permeates live hair cells through a pathway that requires metabotropic P2Y receptor signaling and suggest that phalloidin can be transferred from hair cells to supporting cells in culture.     

Evaluation of postural control in unilateral vestibular hypofunction

IntroductionPatients with vestibular hypofunction, a typical finding in peripheral vestibular disorders, show body balance alterations.ObjectiveTo evaluate the postural control of patients with vertigo and unilateral vestibular hypofunction.MethodThis is a clinical cross-sectional study. Twenty-five patients with vertigo and unilateral vestibular hypofunction and a homogeneous control group consisting of 32 healthy individuals were submitted to a neurotological evaluation including the Tetrax Interactive Balance System posturography in eight different sensory conditions.ResultsFor different positions, vertiginous patients with unilateral vestibular hypofunction showed significantly higher values of general stability index, weight distribution index, right/left and tool/heel synchronizations, Fourier transformation index and fall index than controls.ConclusionIncreased values in the indices of weight distribution, right/left and tool/heel synchronizations, Fourier transformation and fall risk characterize the impairment of postural control in patients with vertigo and unilateral vestibular hypofunction.     

Cognitive processing and body balance in elderly subjects with vestibular dysfunction

Abnormal body balance and cognitive dysfunction may develop in elderly patients with chronic vestibular dysfunction.AimTo evaluate the relationship between cognitive processing and body balance in elderly patients with chronic peripheral vestibular disease. Type of Study: Cross-sectional.MethodsSeventy-six patients (≥ 60 years) with chronic peripheral vestibular dysfunction and dizziness for more than three months were enrolled. The tests for investigating body balance were: the Berg Balance Scale (BBS), Dynamic Gait Index (DGI), Timed Up and Go Test (TUGT) Timed Up and Go Test modified (TUGTm); the Mini Mental State Examination (MMSE), Test Clock (RT,) and Verbal Fluency Test (VF) were applied for assessing cognition.ResultsThe mean age was 69.03 years (SD=6.21 years); most were female (82.9%). There was a significant negative correlation between the MMSE and the TUGT (ρ=-0.312; p=0.01), MMSE and TUGTm (ρ=-0.306; p=0.01), FV and TUGT (ρ=-0.346; p=0.01), and FV and TUGTm (ρ=-0.536; p=0.01); there was a significant positive correlation between the TR and BBS (ρ=0.343; p=0.01), TR and DGI (ρ=0.298; p=0.01), FV and BBS (ρ=0.299; p=0.01), and FV and DGI (ρ=0.306; p=0.01).ConclusionElderly patients with chronic peripheral vestibular disease and worse performance in body balance tests have functional impairment in cognitive skills.     

Motion sickness susceptibility associated with visually induced postural instability and cardiac autonomic responses in healthy subjects

Conclusions This study supports the hypothesis that postural sway and autonomic responses to moving visual stimuli may be associated with motion sickness susceptibility. Characteristics of the cardiac sympathovagal balance during exposure to provocative stimulation may be a marker of individual susceptibility to motion sickness.

Objective To assess the relationship between postural and autonomic responses to a simulated visual motion environment and reported susceptibility to motion sickness.

Material and methods Fifteen healthy subjects were exposed to sinusoidally oscillating visual motion in roll at frequencies of 0.1–0.4 Hz. Recordings were made of postural sway and respiratory frequency and electrocardiograms were obtained from which heart rate variability (HRV) was computed in order to probe cardiac sympathetic and parasympathetic activity.

Results In subjects with a low susceptibility to motion sickness as rated using a standardized questionnaire, there was no significant effect of visual stimulus on postural sway or HRV at any frequency of motion. Subjects with a high susceptibility to motion sickness showed significant postural instability induced by visual stimuli (p<0.01). Visual stimuli presented at a frequency of 0.1 Hz significantly increased the low-frequency power (LF) of HRV, decreased the high-frequency power (HF) of HRV and increased the LF:HF ratio in these subjects (p<0.05).     

Analysis of Joint Power and Work During Gait in Children With and Without Cerebral Palsy

PurposeTo compare joint work in the lower limb joints during different sub-phases of the gait cycle between Cerebral Palsy (CP) and healthy children.MethodsEighteen CP and 20 healthy children’s gait data were collected. The CP group included orthoses, intra-muscular injection of botulinum toxin and surgery groups. A motion capture system was used to collect gait data. Joint work was calculated as positive and negative components in six subphases during gait and normalised by speed when comparing the groups.ResultsThe CP group had a slower walking speed, smaller stride length and longer stance phase than the healthy group. Hip max positive work was 0.12 ± 0.02 Jkg⁻¹/ms⁻¹ for the CP group in pre-mid-stance but 0.07 ± 0.01 Jkg⁻¹/ms⁻¹ for the healthy group during the terminal phase. In terminal stance, ankle positive work was significantly lower in the CP group (0.12 ± 0.01) than in the healthy group (0.18 ± 0.01). The knee showed a similar distribution of positive work in the stance phase for the two groups. In the ankle and hip, the CP group had energy generation mainly in midstance while the healthy group was mainly in terminal stance. In the ankle, the CP group had larger energy absorption in mid-stance than the healthy children group, while the CP group showed lower energy generation in the terminal stance phase than seen in the healthy group.ConclusionThe qualitative and quantitative analysis of joint work provides useful information for clinicians in the treatment and rehabilitation of CP patients.     

Neonatal food restriction permanently alters rat body dimensions and energy intake

Neonatal food restriction (FR) in rats, by means of increased litter size, has been used as a model for developmental programming by several investigators. However, the results reported have been inconsistent and difficult to compare between studies. In the present study, we aim to characterize the effects of this model throughout life in both sexes of one particular strain. On the second day of life, Wistar rat pups were randomly assigned to a litter of 10 (control) or 20 (FR). All litters had an equal number of males and females, and pups were weaned on day 25. Body dimensions and food intake were measured regularly until the age of one year. Serum leptin levels were determined in four subsets of different ages. FR acutely reduced growth in all body dimensions and serum leptin levels. Despite catch-up after weaning, all these parameters remained reduced throughout life. Male and female FR rats had a significantly reduced absolute energy intake throughout life. Male FR rats had significantly higher energy intake adjusted for body weight immediately after weaning. During catch-up growth, both FR males and females showed significantly enhanced feed efficiency. These results suggest that neonatal food restriction programmed both male and female Wistar rats to remain small and lean in adult life, with a lower food intake. Low neonatal leptin levels may play a mechanistic role in this process.