Impact forces in backward falls: Subject-specific video-based rigid body simulation of backward falls

A critical missing component in the study of real-world falls is the ability to accurately determine impact forces resulting from the fall. Subject-specific rigid body dynamic (RBD) models calibrated to video captured falls can quantify impact forces and provide additional insights into injury risk factors. RBD models were developed based on five backward falls captured on surveillance video in long-term care facilities in British Columbia, Canada. Model joint stiffness and initial velocities were calibrated to match the kinematics of the fall and contact forces were calculated. The effect of joint stiffnesses (neck, lumbar spine, hip, and knee joint) on head contact forces were determined by modifying the calibrated stiffness values ±25%. Fall duration, fall trajectories, and maximum velocities showed a close match between fall events and simulations. The maximum value of pelvic velocity difference between Kinovea (an open-source software 2D digitization software) and Madymo multibody modeling was found to be 6% ± 21.58%. Our results demonstrate that neck and hip stiffness values have a non-significant yet large effect on head contact force (t(3) = 1, p = 0.387 and t(3) = 2, p = 0.138), while lower effects were observed for knee stiffness, and the effect of lumbar spine stiffness was negligible. The subject-specific fall simulations constructed from real world video captured falls allow for direct quantification of force outcomes of falls and may have applications in improving the assessment of fall-induced injury risks and injury prevention methods.

Assessing changes in range of motion in adolescent patients undergoing myoActivation® for chronic pain related to myofascial dysfunction: a feasibility study

Introduction

myoActivation® assessment utilizes systemized movement tests to assess for pain and limitations in motion secondary to myofascial dysfunction. myoActivation needling therapy resolves the myofascial components of pain and is associated with immediately observed changes in pain, flexibility, and range of motion. The principal aim of this feasibility study was to objectively characterize the kinematic metrics of upper and lower body motion before and after myoActivation movement tests and therapy.

Methods

Five consecutive eligible adolescent participants considered appropriate for myoActivation were consented to receive their myoActivation intervention in a motion laboratory. Clinical motion analysis was used to measure the changes in maximum range of motion (maxROM) and maximum angular speed to maximum ROM (speedROM) of movement tests predicted to change. Metrics were analyzed to assess changes over specified time intervals - i) baseline to after initial myoActivation session, and ii) baseline to after complete myoActivation course. Each participant served as their own control.

Results

We demonstrated objective evidence of improved maxROM and/or speedROM in 63% of the movement tests predicted to change after just one session of myoActivation and in 77% of movement tests predicted to change over the complete course of treatment. The myoActivation clinician observed positive change in 11/19 of movement tests across all patients, that were predicted to change after the initial myoActivation session; 81% of these positive changes were confirmed by the kinematic data.

Discussion

Clinical motion analysis provides objective support to clinicians evaluating, treating, and teaching myofascial release. A larger, prospective clinical trial is warranted to explore the impact of myoActivation on movement. Refinement of observation techniques and outcome measures established in this feasibility study will strengthen future clinical motion analysis of the myoActivation process.

A survey of stakeholder perspectives on a proposed combined exoskeleton-wheelchair technology

BACKGROUND

Exoskeleton technology has potential benefits for wheelchair users' health and mobility. However, there are practical barriers to their everyday use as a mobility device. In particular, challenges related to travelling longer distances and transitioning between using a wheelchair and exoskeleton walking may present significant deterrents to regular exoskeleton use. In an effort to remove these barriers, a combined exoskeleton-wheelchair concept ('COMBO') has been proposed, which aims to achieve the benefits of both these mobility technologies. Given the inherent importance of including user-stakeholder opinions when designing an assistive technology solution, a study was undertaken to explore the perspectives of wheelchair users and healthcare professionals on the proposed conceptual design of the COMBO.

METHODS

An online survey with quantitative and qualitative components was conducted with wheelchair users and healthcare professionals working directly with individuals with mobility impairments. Respondents rated whether they would use or recommend a COMBO for four potential reasons. Nine design features were rated and compared in terms of their importance. Content analysis was used to analyze data from an open-ended question regarding additional perceptions about using or recommending a COMBO.

RESULTS

A total of 481 survey responses were analyzed, 354 from wheelchair users and 127 from healthcare professionals. Potential health benefits was the most highly rated reason for potential use or recommendation of a COMBO. Of the 9 design features, 2 had a median rating of very important: inclusion of a fall-protection mechanism, and the ability for the operator to use their hands while standing. Qualitative findings indicated that health and physical benefits, use for daily life activities, and psychosocial benefits were important considerations in whether to use or recommend the COMBO.

CONCLUSIONS

This study captures the opinions and perspectives of two stakeholder groups for an exoskeleton-wheelchair hybrid device. It also emphasizes the importance of fall-protection, hand-use capabilities and enabling functional activities. Findings from this study can be utilized to provide insight for the refinement of the COMBO concept, as well as to guide more general mobility device research and development.

Relating Histopathology and Mechanical Strain in Experimental Contusion Spinal Cord Injury in a Rat Model

During traumatic spinal cord injury (SCI), the spinal cord is subject to external displacements that result in damage of neural tissues. These displacements produce complex internal deformations, or strains, of the spinal cord parenchyma. The aim of this study is to determine a relationship between these internal strains during SCI and primary damage to spinal cord gray matter (GM) in an in vivo rat contusion model. Using magnetic resonance imaging and novel image registration methods, we measured three-dimensional (3D) mechanical strain in in vivo rat cervical spinal cord (n = 12) during an imposed contusion injury. We then assessed expression of the neuronal transcription factor, neuronal nuclei (NeuN), in ventral horns of GM (at the epicenter of injury as well as at intervals cranially and caudally), immediately post-injury. We found that minimum principal strain was most strongly correlated with loss of NeuN stain across all animals (R² = 0.19), but varied in strength between individual animals (R² = 0.06–0.52). Craniocaudal distribution of anatomical damage was similar to measured strain distribution. A Monte Carlo simulation was used to assess strain field error, and minimum principal strain (which ranged from 8% to 36% in GM ventral horns) exhibited a standard deviation of 2.6% attributed to the simulated error. This study is the first to measure 3D deformation of the spinal cord and relate it to patterns of ensuing tissue damage in an in vivo model. It provides a platform on which to build future studies addressing the tolerance of spinal cord tissue to mechanical deformation.

Differential Histopathological and Behavioral Outcomes Eight Weeks after Rat Spinal Cord Injury by Contusion, Dislocation, and Distraction Mechanisms

The objective of this study was to compare the long-term histological and behavioral outcomes after spinal cord injury (SCI) induced by one of three distinct biomechanical mechanisms: dislocation, contusion, and distraction. Thirty male Sprague-Dawley rats were randomized to incur a traumatic cervical SCI by one of these three clinically relevant mechanisms. The injured cervical spines were surgically stabilized, and motor function was assessed for the following 8 weeks. The spinal cords were then harvested for histologic analysis. Quantification of white matter sparing using Luxol fast blue staining revealed that dislocation injury caused the greatest overall loss of white matter, both laterally and along the rostrocaudal axis of the injured cord. Distraction caused enlarged extracellular spaces and structural alteration in the white matter but spared the most myelinated axons overall. Contusion caused the most severe loss of myelinated axons in the dorsal white matter. Immunohistochemistry for the neuronal marker NeuN combined with Fluoro Nissl revealed that the dislocation mechanism resulted in the greatest neuronal cell losses in both the ventral and dorsal horns. After the distraction injury mechanism, animals displayed no recovery of grip strength over time, in contrast to the animals subjected to contusion or dislocation injuries. After the dislocation injury mechanism, animals displayed no improvement in the grooming test, in contrast to the animals subjected to contusion or distraction injuries. These data indicate that different SCI mechanisms result in distinct patterns of histopathology and behavioral recovery. Understanding this heterogeneity may be important for the future development of therapeutic interventions that target specific neuropathology after SCI.

Characterization of a Novel, Magnetic Resonance Imaging-Compatible Rodent Model Spinal Cord Injury Device

Rodent models of acute spinal cord injury (SCI) are often used to investigate the effects of injury mechanism, injury speed, and cord displacement magnitude, on the ensuing cascade of biological damage in the cord. However, due to its small size, experimental observations have largely been limited to the gross response of the cord. To properly understand the relationship between mechanical stimulus and biological damage, more information is needed about how the constituent tissues of the cord (i.e., gray and white matter) respond to injurious stimuli. To address this limitation, we developed a novel magnetic resonance imaging (MRI)-compatible test apparatus that can impose either a contusion-type or dislocation-type acute cervical SCI in a rodent model and facilitate MR-imaging of the cervical spinal cord in a 7 T MR scanner. In this study, we present the experimental performance parameters of the MR rig. Utilizing cadaveric specimens and static radiographs, we report contusion magnitude accuracy that for a desired 1.8 mm injury, a nominal 1.78 mm injury (SD = 0.12 mm) was achieved. High-speed video analysis was employed to determine the injury speeds for both mechanisms and were found to be 1147 mm/s (SD = 240 mm/s) and 184 mm/s (SD = 101 mm/s) for contusion and dislocation injuries, respectively. Furthermore, we present qualitative pilot data from a cadaveric trial, employing the MR rig, to show the expected results from future studies.

Combinatorial treatment of acute spinal cord injury with ghrelin, ibuprofen, C16, and ketogenic diet does not result in improved histologic or functional outcome

Because of the complex, multifaceted nature of spinal cord injury (SCI), it is widely believed that a combination of approaches will be superior to individual treatments. Therefore, we employed a rat model of cervical SCI to evaluate the combination of four noninvasive treatments that individually have been reported to be effective for acute SCI during clinically relevant therapeutic time windows. These treatments included ghrelin, ibuprofen, C16, and ketogenic diet (KD). These were selected not only because of their previously reported efficacy in SCI models but also for their potentially different mechanisms of action. The administration of ghrelin, ibuprofen, C16, and KD several hours to days postinjury was based on previous observations by others that each treatment had profound effects on the pathophysiology and functional outcome following SCI. Here we showed that, with the exception of a modest improvement in performance on the Montoya staircase test at 8-10 weeks postinjury, the combinatorial treatment with ghrelin, ibuprofen, C16, and KD did not result in any significant improvements in the rearing test, grooming test, or horizontal ladder. Histologic analysis of the spinal cords did not reveal any significant differences in tissue sparing between treatment and control groups. Although single approaches of ghrelin, ibuprofen, C16, and KD have been reported to be beneficial after SCI, our results show that the combination of the four interventions did not confer significant functional or histological improvements in a cervical model of SCI. Possible interactions among the treatments may have negated their beneficial effects, emphasizing the challenges that have to be addressed when considering combinatorial drug therapies for SCI.

Characterization of a cervical spinal cord hemicontusion injury in mice using the infinite horizon impactor

The majority of clinical spinal cord injuries (SCIs) are contusive and occur at the cervical level of the spinal cord. Most scientists and clinicians agree that the preclinical evaluation of novel candidate treatments should include testing in a cervical SCI contusion model. Because mice are increasingly used because of the availability of genetically engineered lines, we characterized a novel cervical hemicontusion injury in mice using the Infinite Horizon Spinal Cord Impactor (Precisions Systems & Instrumentation, Lexington, KY). In the current study, C57BL/6 mice received a hemicontusion injury of 75 kilodynes with or without dwell time in an attempt to elicit a sustained moderate-to-severe motor deficit. Hemicontusion injuries without dwell time resulted in sustained deficits of the affected forepaw, as revealed by a 3-fold decrease in usage during rearing, a ∼50% reduction in grooming scores, and retrieval of significantly fewer pellets on the Montoya staircase test. Only minor transient deficits were observed in grasping force. CatWalk analysis revealed reduced paw-print size and swing speed of the affected forelimb. Added dwell time of 15 or 30 sec significantly worsened behavioral outcome, and mice demonstrated minimal ability of grasping, paw usage, and overground locomotion. Besides worsening of behavioral deficits, added dwell time also reduced residual white and gray matter at the epicenter and rostral-caudal to the injury, including on the contralateral side of the spinal cord. Taken together, we developed and characterized a new hemicontusion SCI model in mice that produces sufficient and sustained impairments in gross and skilled forelimb function and produced primarily unilateral functional deficits.

Colorimetric assays for quantitative analysis and screening of epoxide hydrolase activity

Focusing on directed evolution to tailor enzymes as usable biocatalysts for fine chemistry, we have studied in detail several colorimetric assays for quantitative analysis of epoxide hydrolase (EH) activity. In particular, two assays have been optimized to characterize variants issued from the directed evolution of the EH from Aspergillus niger. Assays described in this paper are sufficiently reliable for quantitative screening of EH activity in microtiter plates and are low cost alternatives to GC or MS analysis. Moreover, they are usable for various epoxides and not restricted to a type of substrate, such as those amenable to assay by UV absorbancy. They can be used to assay EH activity on any epoxide and to directly assay enantioselectivity when both (R) and (S) substrates are available. The advantages and drawbacks of these two methods to assay EH activity of a large number of natural samples are summarized.

Operationalisation of surveillance of communicable diseases in Chandigarh

Weekly reports of listed communicable diseases from various departments and centres of Government Medical College, Chandigarh, involved in clinical care and laboratory diagnosis, compiled and forwarded by Department of Community Medicine, sub-nodal centre under National Surveillance Programme for Communicable Diseases (NSPCD), to Anti- Malaria-cum-Nodal Officer, NSPCD were analysed for a period of one year Out of 14,082 cases of various communicable diseases 9166 (64.62%) were of Acute Respiratory Infections (ARI), 3586 (25.78%) of Acute Diarrhoeal Diseases (ADDs) and 576 (4.10%) of Pulmonary Tuberculosis. The proportion of ARI appeared higher among females while that of other diseases was higher among males. Most cases of ARI (76.5%) and Pneumonia (3.09%) reported in winter, ADDs (38.89%) and Pulmonary Tuberculosis (4.68%) in summer and Typhoid (1.57%) and Viral Hepatitis (1.23%) in monsoon season. No significant gender predilection was seen. Overall reporting of communicable diseases seen to be significantly more during winter and summer compared to monsoon season, with specific seasonal trends demonstrated by various morbidities.

A spectrophotometric method to assay epoxide hydrolase activity

The Aspergillus niger epoxide hydrolase activity was assayed by spectrophotometric using (rac) p-nitrostryrene oxide (pNSO) as substrate. Both the substrate (pNSO) and the reaction product, p-nitrostryrene diol (pNSD), had a strong absorbance in UV at 280 nm. The assay was based on the measure of the pNSD absorbance of the water phase after extraction of the non-reacted pNSO with a solvent. Among the five solvents tested, chloroform was selected since it extracted more than 99% of the epoxide and only 32% of the produced diol. This extraction yield was independent of the diol and epoxide concentrations and it was fairly reproducible. Using different enzyme amounts, the reaction kinetics were linear for the first 10 min corresponding to degrees of conversion less than 5% for the epoxide. Two controls were run simultaneously, one with the substrate alone (epoxide hydrolysis and non-complete extraction) and one with the enzyme alone (enzyme absorbance at 280 nm). The resulting DeltaOD/min was linear with the amount of enzyme added within a large range from 2 to 80 microg of the EH preparation. The new spectrophotometric assay correlates well with the previous HPLC assay and could be used routinely for an easy and fast evaluation of EH activity. The kinetic parameters of (rac) pNSO hydrolysis by A. niger epoxide hydrolase could be easily determined and K(M) (1.1 mM) compared well with that previously reported (1.0 mM).

H107, a new aminoglycoside anti-Pseudomonas antibiotic produced by a new strain of Spirillospora

Spirillospora spp. (strain 719) has been the source of several antibiotics. One of these designated H107 is produced as a trace. Compared with other antibiotics produced by the same strain, it was obtained only from the broth filtrate after precipitation with acetic acid followed by extraction with n-butanol. It was a water soluble metabolite active against Gram-negative bacteria and especially Pseudomonas spp., and was identified as an aminoglycoside compound. This is the first report of aminoglycoside anti-Pseudomonas production by Spirillospora.

Cardiovascular responses to microinjections of excitatory amino acids into the area postrema of the rat

Although, area postrema (AP) as been implicated in the regulation of cardiovascular function, there is no consensus regarding the type of responses elicited by stimulation of this brain structure. Microinjections (50 nl) of smaller concentrations of excitatory amino acid receptor agonists (e.g., NMDA, KA and trans-ACPD, 10 microM each) into the AP elicited pressor and tachycardic responses in unanesthetized decerebrate as well as urethane-anesthetized rats. Microinjections of higher concentrations (e.g., 50 microM NMDA) of excitatory amino acids (EAAs) into the AP elicited an initial pressor and tachycardic response which was followed by a depressor and bradycardic response; when high concentrations of NMDA were microinjected into the AP, enough concentration may have reached the nucleus tractus solitarius (nTS) to elicit depressor and bradycardic responses. Alternatively, high concentrations of NMDA may excite known projections from AP to the nTS.

Cardiovascular responses to microinjections of glutamate into the nucleus tractus solitarii of unanesthetized supracollicular decerebrate rats

In anesthetized rats, microinjections of excitatory amino acids (EAAs) into the nucleus tractus solitarii (nTS), in a region located immediately rostral to the calamus scriptorius (CS), have been generally reported to elicit depressor and bradycardic responses. On the other hand, in conscious freely moving rats, similar microinjections have been reported to elicit pressor and bradycardic responses. These divergent results have been attributed to the effect of anesthetics. A reinvestigation of the effects of EAAs into the nTS in unanesthetized animals became necessary in order to resolve this controversy. The microinjection technique used in freely moving conscious rats suffers from several technical limitations; for example, microinjections cannot be delivered stereotaxically. In order to avoid these limitations, the present experiments were carried out in unanesthetized supracollicular decerebrate rats. A systematic mapping of nTS in these rats, using microinjections of the solutions of EAAs in artificial cerebrospinal (aCSF) fluid, confirmed that depressor and bradycardic responses are elicited from all the sites in the nTS extending from the CS to a level about 1 mm rostral to it. Pressor responses were elicited by microinjections of l-glutamate (l-Glu) only from the chemoreceptor projection site (a region of the commissural subnucleus, 0.1-0.5 mm caudal to the CS, 0-0.5 mm lateral to the midline and 0.4-0.5 mm deep from the medullary surface). The pressor responses elicited from the aforementioned site were accompanied with bradycardia; this response may be due to diffusion of l-Glu to the dorsal motor nucleus of vagus because the bradycardia disappeared when the depth of the microinjection was reduced to 0.3, instead of 0.5 mm, from the dorsal medullary surface. When urethane was administered intravenously in unanesthetized decerebrate rats, the responses to microinjections of l-Glu remained unchanged, i.e., depressor and bradycardic responses were elicited from all the sites in the nTS extending from the CS to a level about 1 mm rostral to it and pressor and tachycardic responses were elicited from the chemoreceptor projection site. These observations indicated that there is no anesthetic-induced qualitative alteration of the cardiovascular responses to microinjections of EAAs into the nTS.

A new species of Pythium isolated from the Burgundy region in France

Pythium nodosum sp. nov. has been isolated from a soil sample taken in the Burgundy region in France. The fungus has spherical to variously shaped proliferating sporangia, smooth-walled oogonia which are crowded with different antheridial branches making a complicated knot around the former, and aplerotic oospores. Morphological and reproductive aspects of Pythium nodosum as well as the PCR of the internal transcribed spacer (ITS1) of the ribosomal nuclear DNA coupled with restriction fragment length polymorphism analysis are described here. The nucleotide sequences of ITS1 encoding 5.8S rRNA is also given.