No evidence for collateral effects of electromagnetic fields used to increase dissolved oxygen levels on the behavior and physiology of freshwater fishes

Hypoxia in surface waters driven by warming climate and other anthropogenic stressors is a major conservation concern, and technological solutions for water quality remediation are sorely needed. One potential solution involves the use of low-intensity electromagnetic fields (EMFs) to increase dissolved oxygen levels, but potential collateral effects of the EMFs on aquatic animals have not been formally evaluated. We examined the effects of EMF exposure on wild-caught, captive sunfish (Lepomis spp.) over 8-day and 3-day exposures, with and without aeration in mesocosms and stock tanks (respectively). We also quantified ambient fish abundance in close proximity to EMF devices deployed in Opinicon Lake (ON). We found no significant differences in a suite of blood-based stress physiology biomarkers, behaviors, and putative aerobic capacities between EMF and control conditions over 8 days. Aerated mesocosms equipped with activated EMFs consistently had higher oxygen levels in the water than aerated controls. There were no differences in mortality during 3-day oxygen depletion trials under EMF or control conditions, and we detected no differences in fish abundance when the devices were activated in the lake. Our findings suggest that deploying EMF devices in field settings is not likely to exert negative effects on exposed fish populations. PRACTITIONER POINTS: Low-cost, low-energy technological solutions to remediate aquatic hypoxia are sorely needed Electromagnetic fields (EMFs) can increase oxygen flux across air/water interfaces and increase dissolved oxygen levels We found no evidence of negative effects of EMFs on fish physiology or behavior and our results support their use in alleviating hypoxic conditions.

Advances in the development of gene therapy, noncoding RNA, and exosome-based treatments for tendinopathy

Tendinopathy is a common musculoskeletal disorder characterized by chronic low-grade inflammation and tissue degeneration. Tendons have poor innate healing ability and there is currently no cure for tendinopathy. Studies elucidating mechanisms underlying the pathogenesis of tendinopathy and mechanisms mediating the genesis of tendons during development have provided novel targets and strategies to enhance tendon healing and repair. This review summarizes the current understanding and treatments for tendinopathy. The review also highlights recent advances in gene therapy, the potential of noncoding RNAs, such as microRNAs, and exosomes, which are nanometer-sized extracellular vesicles secreted from cells, for the treatment of tendinopathy.

Cycle-dependent matrix remodeling gene expression response in fatigue-loaded rat patellar tendons

Expression profiling of selected matrix remodeling genes was conducted to evaluate differences in molecular response to low-cycle (100) and high-cycle (7,200) sub-failure-fatigue loading of patellar tendons. Using our previously developed in vivo patellar tendon model, tendons were loaded for 100 or 7,200 cycles and expression of selected metalloproteinases (MMPs), tissue inhibitors of metalloproteinases (TIMPs), and collagens were quantified by real-time RT-PCR at 1- and 7-day post-loading. Expression profiles were also obtained from lacerated tendons as an acute injury model. The high-cycle group showed upregulation of TIMP-1, -2, Col3a1, and Col5a1, and downregulation TIMP-4 at both time points, upregulation of MMP-2 at 7-day post-loading and downregulation of MMP-13 and -14 at 1-day post-loading, suggesting overall repair/remodeling. In contrast, the low-cycle loaded group showed upregulation of MMP-2, -3, -13, and Col12a1 at both time points, upregulation of TIMP-1, -2, -3, Col3a1, and integrin β1 and downregulation of integrin α11 at 1-day post-loading and upregulation of Col1a1 at 7-day post-loading, consistent with a hypertrophic (adaptive) pattern. Lacerated tendons showed a typical acute wound response with upregulation of all examined remodeling genes. Differences found in tendon response to high- and low-cycle loading are suggestive of the underlying mechanisms associated with a healthy or damaging response.

Early response to tendon fatigue damage accumulation in a novel in vivo model

This study describes the development and application of a novel rat patellar tendon model of mechanical fatigue for investigating the early in vivo response to tendon subfailure injury. Patellar tendons of adult female Sprague-Dawley rats were fatigue loaded between 1-35N using a custom-designed loading apparatus. Patellar tendons were subjected to Low-, Moderate- or High-level fatigue damage, defined by grip-to-grip strain measurement. Molecular response was compared with that of a laceration-repair injury. Histological analyses showed that progression of tendon fatigue involves formation of localized kinked fiber deformations at Low damage, which increased in density with presence of fiber delaminations at Moderate damage, and fiber angulation and discontinuities at High damage levels. RT-PCR analysis performed at 1- and 3-day post-fatigue showed variable changes in type I, III and V collagen mRNA expression at Low and Moderate damage levels, consistent with clinical findings of tendon pathology and were modest compared with those observed at High damage levels, in which expression of all collagens evaluated were increased markedly. In contrast, only type I collagen expression was elevated at the same time points post-laceration. Findings suggest that cumulative fatigue in tendon invokes a different molecular response than laceration. Further, structural repair may not be initiated until reaching end-stage fatigue life, where the repair response may unable to restore the damaged tendon to its pre-fatigue architecture.

Subrupture tendon fatigue damage

The mechanical and microstructural bases of tendon fatigue, by which damage accumulates and contributes to degradation, are poorly understood. To investigate the tendon fatigue process, rat flexor digitorum longus tendons were cyclically loaded (1-16 N) until reaching one of three levels of fatigue damage, defined as peak clamp-to-clamp strain magnitudes representing key intervals in the fatigue life: i) Low (6.0%-7.0%); ii) Moderate (8.5%-9.5%); and iii) High (11.0%-12.0%). Stiffness, hysteresis, and clamp-to-clamp strain were assessed diagnostically (by cyclic loading at 1-8 N) before and after fatigue loading and following an unloaded recovery period to identify mechanical parameters as measures of damage. Results showed that tendon clamp-to-clamp strain increased from pre- to post-fatigue loading significantly and progressively with the fatigue damage level (p <or= 0.010). In contrast, changes in both stiffness and hysteresis were significant only at the High fatigue level (p <or= 0.043). Correlative microstructural analyses showed that Low level of fatigue was characterized by isolated, transverse patterns of kinked fiber deformations. At higher fatigue levels, tendons exhibited fiber dissociation and localized ruptures of the fibers. Histomorphometric analysis showed that damage area fraction increased significantly with fatigue level (p <or= 0.048). The current findings characterized the sequential, microstructural events that underlie the tendon fatigue process and indicate that tendon deformation can be used to accurately assess the progression of damage accumulation in tendons.

ACL impingement prediction based on MRI scans of individual knees

Although tibial external rotation and abduction do not load the ACL strongly in cadaver-based biomechanical studies, such knee positions are associated with ACL injuries in clinical practice. We hypothesized the ACL could be injured in such knee positions because of its impingement against the intercondylar notch. We developed a three-dimensional geometric ACL impingement model through segmentation of MR images of individual knees. We investigated impingement by determining the deformed geometry and elongation of the ligament as it wrapped around the notch surface during impingement. When impingement did not occur, the gap width separating the ligament and the notch surface was computed. Tibial external rotation/abduction could cause the ACL to impinge against the lateral notch wall and elongate as it wraps around the surface of the notch wall. The impingement occurred between the middle portion of the ligament (at 45% +/- 8% [mean +/- standard deviation] of the ligament length) and the convex surface of the lateral notch wall. Considering the multiband fiber architecture of the ligament, the anteromedial band of the ACL sustained greater elongation during impingement and showed a smaller gap width from the notch surface than the intermediate band or the posterolateral band.

Modeling of ACL impingement against the intercondylar notch

OBJECTIVE

To develop a 3-D mathematical model that accurately evaluates anterior cruciate ligament impingement against the intercondylar notch.

DESIGN

The model simulated physical interactions between the anterior cruciate ligament and the intercondylar notch in tibiofemoral movement.

BACKGROUND

Anterior cruciate ligament impingement has been evaluated through planar radiographic images, which may not characterize the complex 3-D notch shape associated with impingement.

METHODS

After examining potential anterior cruciate ligament impingement in five cadaver knee specimens, the model was implemented using data from an individual cadaveric knee with representative impingement. The knee was loaded passively in various patterns to induce impingement, and the impingement force and six degrees-of-freedom tibiofemoral kinematics were measured. The femur, tibia, and anterior cruciate ligament were digitized. Spatial data points representing the notch surfaces were surface-fitted using bicubic splines. The model detected for impingement during the tibiofemoral movement and used a "crawling algorithm" to determine the deformed geometry of the impinging ligament.

RESULTS

The model detected the impingement accurately and the ligament strain determined by the model was highly correlated with the recorded impingement force when impingement occurred during the tibiofemoral movement. Distance between the anterior cruciate ligament and the notch wall was determined when impingement was not detected.

CONCLUSION

The model quantitatively characterized impingement of the anterior cruciate ligament against the intercondylar notch in 3-D space.

RELEVANCE

The approach helps us better understand anterior cruciate ligament injury mechanisms in individual knees. Clinically, the model could potentially be used to analyze subject-specific potential/actual anterior cruciate ligament impingement based on the subject's MRI scans.

Myxoid change in malignant lymphoma. Pathogenetic considerations

Myxoid change is a rare phenomenon in malignant lymphoma, and its pathogenesis is not well understood. We present a case of large B-cell lymphoma of the small bowel in which myxoid change is confined to one of the regional lymph nodes involved by lymphoma. An increase of vimentin-positive mesenchymal cells in the myxoid zones compared with the nonmyxoid areas within the lymph node and a complete lack of myxoid change in the tumor occurring in other sites of this case suggest that the myxoid stroma results from some local factors (most probably tissue edema) stimulating proliferation of fibroblasts/myofibroblasts.

Effect of bite force on the masseteric electromyographic silent period in man

The duration of the masseteric EMG silent period as induced by tapping on the chin was measured at different levels of sustained bite force. Under both open bite and normal occlusion, the duration of the silent period was inversely related to the magnitude of the bite force. For bite force of the same magnitude, the value of the silent period remained relatively constant for the same subject in different trials (SEM congruent to 1 per cent), whereas the absolute values of the silent periods ranged far and wide for different individuals even under similar experimental conditions.

Correlative study of pain perception and masticatory muscle reflexes in man

An attempt was made to explore the possibility of using the masticatory muscle reflexes as pain indices in human subjects. It was found that the digastric reflex, so readily evoked by electrodental stimulation in experimental animals, could not be consistently elicited in man. The reflex silent period of the masseteric muscles, on the other hand, may be used as a pain index for evaluating dental analgesia, provided that analgesic interference is anticipated at points along the reflex arc.

An experimental evaluation of regionally induced analgesia in dentistry

A method for the assessment of induced regional dental analgesia in experimental animals is described. It is based on the validity of the electrodentally elicited digastric electromyogram as a pain index. This method has been applied to study the effectiveness of one local anesthetic and of "electroacupuncture" to suppress pain regionally.