Center of mass-based posturography for free living environment applications.

BACKGROUND: Postural assessment is crucial as risk of falling is a major health problem for the elderly. The most widely used devices are force and balance plates, while center of pressure is the most studied parameter as measure of neuromuscular imbalances of the body sway. In out-of-laboratory conditions, where the use of plates is unattainable, the center of mass can serve as an alternative. This work proposes a center of mass-based posturographic measurement for free living applications. METHODS: Ten healthy and ten Parkinson's disease individuals (age = 26.1 ± 1.5, 70.4 ± 6.2 years, body mass index = 21.7 ± 2.2, 27.6 ± 2.8 kg/m2, respectively) participated in the study. A stereophotogrammetric system and a force plate were used to acquire the center of pressure and the 5th lumbar vertebra displacements during the Romberg test. The center of mass was estimated using anthropometric measures. Posturographic parameters were extracted from center of pressure, center of mass and 5th lumbar vertebra trajectories. Normalized root mean squared difference was used as metric to compare the trajectories; Spearman's correlation coefficient was computed among the posturographic parameters. FINDINGS: Low values of the metric indicated a good agreement between 5th lumbar vertebra trajectory and both center of pressure and center of mass trajectories. Statistically significant correlations were found among the postural variables. INTERPRETATION: A method to perform posturography tracking the movement of the 5th lumbar vertebra as an approximation of center of mass has been presented and validated. The method requires the solely kinematic tracking of one anatomical landmark with no need of plates for free living applications.

Influence of different calibration methods on surface electromyography-informed musculoskeletal models with few input signals.

BACKGROUND: Although model personalization is critical when assessing individuals with morphological or neurological abnormalities, or even non-disabled subjects, its translation into routine clinical settings is hampered by the cumbersomeness of experimental data acquisition and lack of resources, which are linked to high costs and long processing pipelines. Quantifying the impact of neglecting subject-specific information in simulations that aim to estimate muscle forces with surface electromyography informed modeling approaches, can address their potential in relevant clinical questions. The present study investigates how different methods to fine-tune subject-specific neuromuscular parameters, reducing the number of electromyography input data, could affect the estimation of the unmeasured excitations and the musculotendon forces. METHODS: Three-dimensional motion analysis was performed on 8 non-disabled adult subjects and 13 electromyographic signals captured. Four neuromusculoskeletal models were created for 8 participants: a reference model driven by a large set of sEMG signals; two models informed by four electromyographic signals but calibrated in different fashions; a model based on static optimization. FINDINGS: The electromyography-informed models better predicted experimental excitations, including the unmeasured ones. The model based on static optimization obtained less reliable predictions of the experimental data. When comparing the different reduced models, no major differences were observed, suggesting that the less complex model may suffice for predicting muscle forces with a small set of input in clinical gait analysis tasks. INTERPRETATION: Quantitative model performance evaluation in different conditions provides an objective indication of which method yields the most accurate prediction when a small set of electromyographic recordings is available.

Heparin enhances protamine disulfide bond reduction during in vitro decondensation of human spermatozoa.

BACKGROUND: Human sperm nuclear decondensation in vivo involves protamine disulfide bond reduction by glutathione (GSH) and protamine/histone exchange, presumably with heparan sulfate (HS) as the protamine acceptor. The aim of the present study was to test the hypothesis that these two events occur simultaneously rather than sequentially, as has been hitherto accepted, and to test for the presence of HS in the human oocyte. METHODS: Spermatozoa and isolated sperm nuclei obtained from normal volunteers were exposed in vitro to heparin, the functional analogue of HS and either GSH or dithiothreitol (DTT) as the disulfide reducing agent. Decondensing reagents were added either simultaneously or sequentially. Percentage sperm nuclear decondensation was assayed by phase contrast microscopy. Thiol reduced status of isolated sperm nuclei was evaluated both indirectly [acridine orange (AO) staining of acid-denatured DNA] and directly [monobromobimane (mBBr) staining of protamine-free thiols]. The presence of HS in mature metaphase II (MII) human oocytes was analyzed by immunocytochemistry. RESULTS: Sequential addition of reagents always resulted in significantly lower decondensation if GSH was used as the disulfide bond reducer (P < 0.05 for sperm and P < 0.001 for nuclei), but only when heparin was used first, when DTT was the disulfide reducing agent (P < 0.05 for sperm and P < 0.01 for nuclei). Both AO staining of DNA and mBBr staining of protamines revealed that the addition of heparin to GSH but not to DTT significantly increased the thiol reduced status of sperm chromatin. HS was detected in the ooplasm of zona-free MII human oocytes. CONCLUSIONS: The results presented in this paper clearly show that heparin enhances the sperm chromatin thiol reducing activity of GSH in vitro, suggesting that in vivo thiol reduction and protamine/histone exchange could occur as simultaneous, rather than sequential, events. We also demonstrate for the first time the presence of HS in the human oocyte.

Quantitative assessment of training effects using EksoGT® exoskeleton in Parkinson's disease patients: A randomized single blind clinical trial.

Background: Gait alterations are among the most disabling motor-symptoms associated with Parkinson's Disease (PD): reduced stride length, stride velocity and lower limb joint range of motion are hallmarks of parkinsonian gait. Research focusing on optimal functional rehabilitation methods has been directed towards powered lower-limb exoskeletons which combines the advantages delivered from the grounded robotic devices with the ability to train the patient in a real-world environment. As gait involves both central (CNS) and peripheral nervous systems (PNS), targeted rehabilitation must restore not only mechanics but also neurophysiological gait patterns. Methods: Two cohorts of subjects will be enrolled and equally distributed between one group (n = 25) who will undergo a functional kinematic therapy, and one group (n = 25) who will undergo an overground wearable-exoskeleton training. Participants are evaluated at three time points: before the therapy (T0), after the therapy (T1), 4-weeks after T1 (T2). Comprehensive gait analysis and surface electromyography will be combined into neuromusculoskeletal modelling to determine modifications at the PNS level. Functional magnetic resonance imaging coupled with electroencephalography will be used to determine modifications at the CNS level. Conclusion: The findings of the proposed trial will likely give substantial solutions for the management of gait and postural disorders in PD where valid interventions are lacking. The coupling of movement evaluation, which assesses neuromuscular and biomechanical features, with neurological data, will better define the impact of the therapy on the relationship between PD motor alterations and brain activity. This will provide an active treatment that is personalized and shared to large populations.

Different perspectives in understanding muscle functions in Parkinson's disease through surface electromyography: Exploring multiple activation patterns.

Gait disorders are one of the cardinal features of Parkinson's Disease (PD) and might be affected by a modified pattern of motor unit activation. This work explores how PD affects the lower limb muscle control and how muscle activity contributes to gait impairment. Using clinical gait analysis data, the onset and the offset of the surface electromyographic (sEMG) signal of four lower limb muscles were determined in 18 people with PD and compared with 10 heathy controls. Different motor patterns were identified in both the populations through a statistical detector algorithm and described in terms of linear envelope, local maxima activation magnitude and occurrence, co-contractions, and bursts duration. Statistical analysis was performed using statistical parametric mapping for the sEMG envelope and linear mixed effects models for the sEMG parameters. An equivalent number of sEMG patterns was detected in PD with respect to controls. Significant differences were highlighted between the two cohorts within the same activation modality. Plantarflexors muscles activation was delayed on time and had different durations and activations peaks, while Biceps Femoris revealed a higher local maximum. These results suggested that functional tibiotarsus joint reeducation coupled with postural rehabilitation might be beneficial for people with PD.

The presence of heparan sulfate in the mammalian oocyte provides a clue to human sperm nuclear decondensation in vivo.

BACKGROUND: Previous results from our laboratory have led us to propose heparan sulfate (HS) as a putative protamine acceptor during human sperm decondensation in vivo. The aim of this paper was to investigate the presence of glycosaminoglycans in the mammalian oocyte in an effort to better support this contention. METHODS: Two experimental approaches are used: oocyte labeling to identify the presence of HS and analysis of sperm decondensing ability of fresh oocytes in the presence or absence of specific glycosidases. RESULTS: Staining of mouse zona-intact oocytes with the fluorescent cationic dye, Rubipy, at pH 1.5 allowed for the detection of sulfate residues in the ooplasm by confocal microscopy. HS was detected in the ooplasm by immunocytochemistry. A sperm decondensation microassay using heparin and glutathione was successfully developed. The same level of sperm decondensation could be attained when heparin was replaced by mouse zona-free oocytes. Addition of heparinase to the oocyte/glutathione mixture significantly reduced sperm decondensation (P = 0.0159), while there was no effect following addition of either chondroitinase ABC or hyaluronidase. CONCLUSIONS: The results presented in this paper demonstrate for the first time that HS is present in the mammalian oocyte and show that HS is necessary for fresh oocytes to express their sperm decondensing ability in vitro.

In vitro effects of endosulfan-based insecticides on mammalian sperm.

Endosulfan is an organochloride insecticide extensively used in several countries to protect crops from pests. As several studies indicate that endosulfan can affect human and animal development, the aim of this study was to analyse whether sperm parameters and the process of chromatin decondensation could be altered by endosulfan in mice sperm. Spermatozoa from cauda epididymis were obtained from mature male mice and incubated in the presence of two commercial formulations (CFs) of endosulfan (Master® and Zebra Ciagro®) or the active ingredient (AI) alone. A significant decrease in the percentage motility and viability of spermatozoa with respect to controls was found. In vitro decondensation was performed in the presence of glutathione and heparin. Spermatozoa incubated with the AI, endosulfan Master® and endosulfan Zebra Ciagro® showed an increase in chromatin decondensation. In addition, the TUNEL assay showed that DNA fragmentation was significantly higher when sperm were incubated with either one of the CFs when compared to the AI or controls. The ultrastructure analysis of sperm cells showed evident changes in the structure of the plasma and acrosome membranes of sperm incubated with endosulfan AI or the CFs. These results suggest that endosulfan can affect sperm integrity and in vitro chromatin decondensation as well as DNA fragmentation.