Human sperm rotate with a conserved direction during free swimming in four dimensions

Head rotation in human spermatozoa is essential for different swimming modes and fertilisation, as it links the molecular workings of the flagellar beat with sperm motion in three-dimensional (3D) space over time. Determining the direction of head rotation has been hindered by the symmetry and translucent nature of the sperm head, and by the fast 3D motion driven by the helical flagellar beat. Analysis has been mostly restricted to two-dimensional (2D) single focal plane image analysis, which enables tracking of head centre position but not tracking of head rotation. Despite the conserved helical beating of the human sperm flagellum, human sperm head rotation has been reported to be uni- or bi-directional, and even to intermittently change direction in a given cell. Here, we directly measure the head rotation of freely swimming human sperm using multi-plane 4D (3D+t) microscopy and show that: (1) 2D microscopy is unable to distinguish head rotation direction in human spermatozoa; (2) head rotation direction in non-capacitating and capacitating solutions, for both aqueous and viscous media, is counterclockwise (CCW), as seen from head to tail, in all rotating spermatozoa, regardless of the experimental conditions; and (3) head rotation is suppressed in 36% of spermatozoa swimming in non-capacitating viscous medium, although CCW rotation is recovered after incubation in capacitating conditions within the same viscous medium, possibly unveiling an unexplored aspect of the essential need of capacitation for fertilisation. Our observations show that the CCW head rotation in human sperm is conserved. It constitutes a robust and persistent helical driving mechanism that influences sperm navigation in 3D space over time, and thus is of critical importance in cell motility, propulsion of flagellated microorganisms, sperm motility assessments, human reproduction research, and self-organisation of flagellar beating patterns and swimming in 3D space.

Inability to suppress head rotation during the saccade test as a clinical biomarker for cognitive dysfunction in Parkinson's disease

BACKGROUND

There is a need for development of reliable and accessible clinical biomarker for detecting cognitive dysfunction in PD. This study aimed to investigate whether involuntary head rotation during the saccade test could serve as a potential biomarker for screening cognitive dysfunction in PD.

METHODS

A total of 27 PD patients and nine age- and sex-matched healthy controls were prospectively enrolled in this study. A custom-designed gyroscope was attached to the forehead of each participant, and a saccade test consisting of 20 trials was conducted. The entire test was recorded on video, and two movement disorder experts independently rated the degree of head rotation, blinded to the patients' clinical information. The peak angular velocity of head rotation was derived from the gyroscope data. Participants underwent Montreal Cognitive Assessment (MoCA) as the cognitive evaluation. Correlation analysis was performed to assess the relationship between head rotation and MoCA scores.

RESULTS

The mean peak angular velocity of head rotation significantly correlated with the MoCA scores (R = -0.52, p = 0.0023) including age, sex, disease duration, and education duration as cofactors. The optimal peak angular velocity thresholds for head rotation, which aligned with the manual ratings, were determined to be 5°/s and 10°/s for raters 1 and 2, respectively. The MoCA scores exhibited significant correlations with the number of head rotations, using both the 5°/s (R = -0.36, p = 0.042) and 10°/s (R = -0.49, p = 0.0048) thresholds. Furthermore, the mean angular velocity of the head demonstrated a 100% positive predictive value and specificity for the detection of cognitive impairment (MoCA < 26), based on the cut-offs of 5°/s and 10°/s.

CONCLUSION

Inability to suppress head rotation during saccades may serve as a potential clinical biomarker for screening cognitive dysfunction in PD.

The effect of head rotation on OSA is associated with disease severity: a cross-sectional study

PURPOSE

Head rotation is an effective positional therapy for obstructive sleep apnea (OSA). However, not all OSA patients benefit from head rotation. This study aimed to explore the clinical phenotype of OSA patients who can benefit from head rotation.

METHODS

We performed a retrospective review of 184 consecutive OSA patients who underwent polysomnography. Head rotation in supine position was determined by high-quality video recording. According to the changes in apnea-hypopnea index (AHI) after head rotation, OSA patients were divided into two groups: patients with response to head rotation(HR) and patients without response to head rotation(NHR). Demographic factors and overnight polysomnography were analyzed.

RESULTS

Compared with NHR group, HR group showed significantly lower AHI (51.8 vs 31.5, p < 0.01), time spent with oxygen saturation below 90%(5.3% vs 0.51%, p < 0.01), and higher lowest oxygen saturation(80% vs 86%, p < 0.05). Logistic regression showed that AHI was an independent factor to predict the decrease of AHI in head rotation (OR 0.985, 95% CI 0.970-0.979, p < 0.05). Among mild to moderate group (AHI < 30/h), severe group (30/h ≤ AHI < 60/h), and extremely severe group (AHI ≥ 60/h), the percentage decrease of AHI in head rotation was 18.5%, 9.5%, and 2.6%, respectively. Surprisingly, the percentage decrease of AHI of 6 responders in mild to moderate group was more than 50%.

CONCLUSION

OSA patients who respond well to head rotation have less severe disease, and patients with mild to moderate OSA are more likely to improve and benefit from this position. Our research provides potential strategies and insights into the individual treatment of OSA patients.

Keeping balance during head-free smooth pursuit: The role of aging

Standing balance is often more unstable when visually pursuing a moving target than when fixating on a stationary one. These effects are common in both young and older adults when the head is restrained during visual task performance. The present study focused on the role of head motion on standing balance during smooth pursuit as a function of age. Three predictions were tested: a) standing balance is compromised to a greater extent in older than young adults by gaze target pursuit compared to fixation, b) older adults pursue a moving target with greater and more variable head rotation than young adults, and c) greater and more variable head rotation during the smooth pursuit task is associated with greater Center of Pressure (CoP) sway. Twenty-two (22) older (age: 71.7 ± 8.1, 12 M / 10 F) and twenty-three (23) young adults (age: 23.6 ± 2.5, 12 M / 11 F) stood on a force plate while either fixating a stationary or smoothly pursuing a horizontally moving target (31.9° peak-to-peak visual angle). CoP (Bertec Balance Plate), head kinematics (Vicon Motion Analysis) and head-unconstrained gaze (Pupil Labs Invisible) were synchronously recorded. The root means square (RMS) of CoP velocity increased during smooth pursuit compared to fixation regardless of age (p < .05), while the interquartile CoP range increased only in older and not in young participants (p < .05). We also calculated the head rotation range (peak to peak cycle amplitude) of motion and variability (SD of range of motion) across the cycles of the smooth pursuit task. Older adults pursued the moving target employing more variable (p = .022) head yaw rotation than young participants although the mean range of head rotation was similar between groups (p =. 077). The amplitude and variability of head yaw rotation did not correlate with CoP sway measures. Results suggest that head-free pursuing of a moving target decreased balance to a greater extent in old than young individuals when compared to fixation. Nevertheless, postural sway during head-free smooth pursuit was not associated with the extent or variability of head rotation.

Regional oxygenation, perfusion and body and/or head position: Are preterm infants adversely impacted? A systematic review

This review addresses regional oxygenation and perfusion changes for preterm infants and changes with body position, with or without head rotation. Future directions for improving neurodevelopmental and clinical outcomes are suggested. The MEDLINE, Embase and Scopus databases were searched up to July 2021. Fifteen out of 470 studies met the inclusion criteria. All were prospective, observational studies with a moderate risk of bias. Significant variation was found for the baseline characteristics of the cohort, postnatal ages, and respiratory support status at the time of monitoring. When placed in a non-supine position, preterm infants showed a transient reduction in cardiac output and stroke volume without changes to heart rate or blood pressure. No studies reported on long-term neurodevelopmental outcomes. Overall, side lying or prone position does not appear to adversely affect regional, and specifically cerebral, oxygenation or cerebral perfusion. The effect of head rotation on regional oxygenation and perfusion remains unclear.

Ultrasound during neck rotation to reveal a case of positional occlusion of the internal carotid artery

Positional occlusion of the internal carotid artery is an unusual phenomenon. Reports are scarce in the literature and generally related to compression by external agents when the head is rotated. Cases with no extrinsic etiology are even more uncommon and require high suspicion to avoid misdiagnosis. We present a case of a patient with intermittent internal carotid occlusion depending on the position of the head with no external agent identified. Due to the dynamic characteristics of this presentation, diagnostic tests yielded contradictory results. Carotid ultrasound during neck rotation revealed the positional occlusion. Ultrasound is a versatile technique to explore the carotid arteries in different angles of the neck, useful if positional pathology is suspected.

Resolving front-back ambiguity with head rotation: The role of level dynamics

Making small head movements facilitates spatial hearing by resolving front-back confusions, otherwise common in free field sound source localization. The changes in interaural time difference (ITD) in response to head rotation provide a robust front-back cue, but whether interaural level difference (ILD) can be used as a dynamic cue is not clear. Therefore, the purpose of the present study was to assess the usefulness of dynamic ILD as a localization cue. The results show that human listeners were capable of correctly indicating the front-back dimension of high-frequency sinusoids based on level dynamics in free field conditions, but only if a wide movement range was allowed (±40^∘). When the free field conditions were replaced by simplistic headphone stimulation, front-back responses were in agreement with the simulated source directions even with relatively small movement ranges (±5^∘), whenever monaural sound level and ILD changed monotonically in response to head rotation. In conclusion, human listeners can use level dynamics as a front-back localization cue when the dynamics are monotonic. However, in free field conditions and particularly for narrowband target signals, this is often not the case. Therefore, the primary limiting factor in the use of dynamic level cues resides in the acoustic domain behavior of the cue itself, rather than in potential processing limitations or strategies of the human auditory system.

A study on asymmetry in infants with congenital muscular torticollis according to head rotation

[Purpose] The purpose of this study was to research asymmetry in infants with congenital muscular torticollis (CMT) according to head rotation. [Subjects and Methods] 70 infants with CMT were divided into grade I, grade II, and grade III according to the asymmetry of cervical rotation. Patients received ultrasound and massage therapy for 30 minutes, in conjunction with passive stretching exercises, 3 times a week. Repeated measurement results from interventions were presented from baseline, 3 months, and 6 months. Asymmetry was evaluated by head tilt (HT) and the torticollis overall assessment (TOA). [Results] The TOA measured at 3 months and 6 months showed a significant difference in inter group scores and an intra group interaction with grade and rating scale was observed. In contrast, HT was significantly different in intra group comparison, but no significant difference in inter and intra group interaction was observed in the angle and grade. [Conclusion] Conservative physical therapy showed lasting effects according to the intervention period over 3 months and 6 months of repeated measurements over time in TOA and HT. Especially, TOA showed significant differences in asymmetric changes according to the cervical rotation.

Assessment of Image Distortion from Head Rotation in Lateral Cephalometry

BACKGROUND

The patient's head can be slightly rotated sagitally vertically or transversely within the head holding device. Because of such improper positions due to the head rotation, an error can occur in cephalometric measurements. The purpose of this study was to identify the potential projection errors of lateral cephalometric radiograph due to head rotation toward X-ray film in the vertical Z-axis.

MATERIALS AND METHODS

Totally, 10 human dry skulls with permanent dentition were collected from the Department of Anatomy, J.J.M.C. Medical College, Davanagere. Each dry skull was rotated from 0° to -20° at 5° intervals. A vertical axis, the Z-axis, was used as a rotational axis to have 100 lateral cephalometric radiographs exposed. Four linear (S-N, Go-Me, N-Me, S-Go) and six angular measurements (SNA, SNB, N-S-Ar, S-Ar-Go, Ar-Go-Me, AB-Mandibular plane angle) were calculated manually.

RESULTS

The findings were that: (1) Angular measurements have fewer projection errors than linear measurements; (2) the greater the number of landmarks on the midsagittal plane that are included in angular measurements, the fewer the projection errors occurring; (3) the horizontal linear measurements have more projection errors than vertical linear measurements according to head rotation.

CONCLUSION

In summary the angular measurements of lateral cephalometric radiographs are more useful than linear measurements in minimizing the projection errors associated with head rotation on a vertical axis.

Peripheral refraction with eye and head rotation with contact lenses

PURPOSE

To evaluate the impact of eye and head rotation in the measurement of peripheral refraction with an open-field autorefractometer in myopic eyes wearing two different center-distance designs of multifocal contact lenses (MFCLs).

METHODS

Nineteen right eyes from 19 myopic patients (average central M ± SD = -2.67 ± 1.66 D) aged 20-27 years (mean ± SD = 23.2 ± 3.3 years) were evaluated using a Grand-Seiko autorefractometer. Patients were fitted with one multifocal aspheric center-distance contact lens (Biofinity Multifocal D(®)) and with one multi-concentric MFCL (Acuvue Oasys for Presbyopia). Axial and peripheral refraction were evaluated by eye rotation and by head rotation under naked eye condition and with each MFCL fitted randomly and in independent sessions.

RESULTS

For the naked eye, refractive pattern (M, J0 and J45) across the central 60° of the horizontal visual field values did not show significant changes measured by rotating the eye or rotating the head (p > 0.05). Similar results were obtained wearing the Biofinity D, for both testing methods, no obtaining significant differences to M, J0 and J45 values (p > 0.05). For Acuvue Oasys for presbyopia, also no differences were found when comparing measurements obtained by eye and head rotation (p > 0.05). Multivariate analysis did not showed a significant interaction between testing method and lens type neither with measuring locations (MANOVA, p > 0.05). There were significant differences in M and J0 values between naked eyes and each MFCL.

CONCLUSION

Measurements of peripheral refraction by rotating the eye or rotating the head in myopic patients wearing dominant design or multi-concentric multifocal silicone hydrogel contact lens are comparable.

The effect of head rotation on efficiency of ventilation and cuff pressure using the PLMA in pediatric patients

Background

This study examined whether changing the head position from neutral to side can affect expiratory tidal volume (TV) and cuff pressure when the appropriate sizes of a Proseal™ Laryngeal Mask Airway (PLMA)-depending on the body weight -are used in pediatric patients during pressure controlled ventilation (PCV).

Methods

Seventy-seven children (5-30 kg) were divided into three groups according to their body weight, PLMA#1.5 (group I, n = 24), #2 (group II, n = 26), and #2.5 (group III, n = 27). After anesthesia induction, a PLMA was placed with a cuff-pressure of 60 cmH₂O. The TV and existence of leakage at the peak inspiratory pressure (PIP) of 20 cmH₂O, and the appropriate PIP for TV 10 ml/kg were examined. Upon head rotation to the left side, the TV, PIP, cuff pressure changes, and the appropriate PIP to achieve a TV 10 ml/kg were evaluated.

Results

Head rotation of 45 degrees to the left side during PCV caused a significant increase in cuff pressure and a decrease in TV, and there was no definite leakage. Changes in PIP and TV were similar in the three groups. The cuff pressure increased but there was no significant difference between the three groups.

Conclusions

Although cuff pressure and TV of the PLMA were changed significantly after turning the head from the neutral position to the side, a re-adjustment of the cuff pressure and PIP to maintain a TV of 10 ml/kg can make the placed PLMA useful and successful in pediatric patients under general anesthesia.