Males of the androdioecious species Caenorhabditis elegans are more likely to attempt to mate with and successfully inseminate C. elegans hermaphrodites that do not concurrently harbor sperm. Although a small number of genes have been implicated in this effect, the mechanism by which it arises remains unknown. In the context of the battle of the sexes, it is also unknown whether this effect is to the benefit of the male, the hermaphrodite, or both. We report that successful contact between mature sperm and oocyte in the C. elegans gonad at the start of fertilization causes the oocyte to release a signal that is transmitted to somatic cells in its mother, with the ultimate effect of reducing her attractiveness to males. Changes in hermaphrodite attractiveness are tied to the production of a volatile pheromone, the first such pheromone described in C. elegans.fertilization | sex pheromones | egg-soma communication I ts properties of self-fertilization and rapid generation, along with its extensive library of mutants, make Caenorhabditis elegans an excellent system in which to study reproductive events. The generation time of C. elegans is under 3 d, and a single hermaphroditic worm can use its sperm to fertilize its own eggs, without the need for mating (1). C. elegans and related nematodes have a robust sperm sensation pathway that limits unfruitful oocyte maturation and ovulation (2). Both self-sperm and nonself-sperm secrete protein ligands, known as major sperm proteins (MSPs), that activate signal transduction pathways in both unfertilized oocytes, leading to activation of mitogen-activated protein kinase (MPK-1), and the somatic gonad, involving transcription factor CEH-18. The result of this signaling is the release of oocytes from prophase I arrest and the ovulation of unarrested oocytes into the uterus (3, 4).Several behaviors of female and hermaphroditic nematodes have been demonstrated to correlate with either the presence of sperm or the recentness of mating. C. elegans hermaphrodites that have exhausted their supply of self-sperm are more likely to elicit a mating response from males of their species, and less likely to resist an attempted mating. Mutant C. elegans hermaphrodites that develop without self-sperm also elicit more mating attempts, and this increase in attractiveness vanishes after a successful mating (5, 6). In the gonochoristic species Caenorhabditis brenneri and Caenorhabditis remanei, males are attracted to a volatile pheromone produced only by females that have not recently mated (7). The mechanisms that link these behaviors to sperm status remain unknown.Pheromones have been shown to exist in dozens of nematode species (8-10) and have been positively identified in several, including C. elegans (11-14). Although HPLC-MS studies have led to the identification of more than 140 pheromones and pheromone-related metabolites in C. elegans (15), little is known about how production of such pheromones is regulated. Life stage and environmental conditions have been shown to affect pheromone o...
Research has shown that the surrounding biomechanical environment plays a significant role in the development, differentiation, repair, and degradation of tendon, but the interactions between tendon cells and the forces they experience are complex. In vitro mechanical stimulation models attempt to understand the effects of mechanical load on tendon and connective tissue progenitor cells. This article reviews multiple mechanical stimulation models used to study tendon mechanobiology and provides an overview of the current progress in modelling the complex native biomechanical environment of tendon. Though great strides have been made in advancing the understanding of the role of mechanical stimulation in tendon development, damage, and repair, there exists no ideal in vitro model. Further comparative studies and careful consideration of loading parameters, cell populations, and biochemical additives may further offer new insight into an ideal model for the support of tendon regeneration studies.
Objectives: The spread of the coronavirus disease 2019 (COVID-19) in February and March of 2020 led to the delay or cancellation of major sporting leagues and events across the globe. Collegiate athletic competitions were postponed until the end of the 2020 calendar year and organized collegiate athletic practices and training camps throughout 2020 were either cancelled or significantly reduced in frequency. The impact of the COVID-19 pandemic on injury epidemiology in collegiate athletics has not yet been investigated. We aim to describe the types of athletic injuries sustained by high level collegiate athletes before and after the COVID-19 pandemic. Methods: The Pacific 12 (Pac-12) Health Analytics Program contains all injuries sustained by intercollegiate athletes in the Pac-12 conference. This database was queried for injuries that occurred across all sports from January 2019 to June 2021. For all sports, timing of injury onset (acute versus overuse), severity of injury, rate of procedural intervention, injury mechanism (contact versus non-contact), and likelihood of injury during the 4th quarter of competition (final 25% of competition) was compared between the season immediately preceding the COVID-19 pandemic and the season immediately after. In this database, injury timing is defined as overuse if symptom onset occurred more than 24 hours after the precipitating incident. Results were stratified by upper and lower extremity as well as sport. Sub group analyses were also performed on knee and shoulder injuries among athletes competing in sports with historically high rates of knee and shoulder injuries. Multivariate analysis including gender was performed. Results: A total of 12,319 sport-related injuries across 23 sports were identified. The overall proportion of injuries sustained during the 4th quarter of competition was higher in the post-pandemic season (28.5% vs. 25.9%, p=0.015) and the overall proportion of non-contact injury was higher in the post-pandemic season (46.1% vs. 39.8%, p<0.0001). These findings were replicated when stratifying by upper and lower extremity injury. In sports with traditionally high rates of knee injuries (football, soccer, basketball, lacrosse, gymnastics), there was a higher proportion of overuse knee injuries (21.2% vs. 14.5%, p=0.003) and a higher proportion of non-contact knee injuries (47.6% vs 37.4%, p<0.0001) sustained in the post-pandemic season. In sports with high rates of shoulder injuries (football, baseball, softball, gymnastics, swimming, volleyball), there was a higher proportion of shoulder injuries taking place in the final 25% of competition (27.2% vs. 18.8%, p=0.016)) and a higher proportion of non-contact shoulder injuries (37.6% vs. 24.9%, p<0.0001) sustained in the post-pandemic season. Multivariate analysis also demonstrated higher rates of non-contact (OR 1.28, p<0.0001) and overuse injuries (OR 1.30, p=0.001) observed in the post-pandemic season and showed that female gender was significantly associated with overuse injury (OR 1.92, p<0.0001), non-contact injury (OR 1.35, p<0.0001), season ending injury (OR 2.33, p=0.008), and decreased likelihood of procedural intervention (OR 0.55, p<0.0001). Conclusions: Compared with the season immediately preceding the COVID-19 pandemic, athletes competing in the post-pandemic season were at higher risk of non-contact injury and injury near the end of a competition. There was a higher risk of overuse knee injuries and non-contact knee and shoulder injuries in the post-pandemic season. These findings are the first to describe the effect of a global pandemic on an athlete’s injury risk profile upon return to sport and may be used to guide decisions regarding athlete workload and training. [Table: see text][Table: see text][Table: see text]
Background: The coronavirus disease 2019 (COVID-19) pandemic significantly disrupted athletic activities, including those in the Pacific 12 (Pac-12) Conference of the National Collegiate Athletic Association. It is currently unknown how the disruption in training and competition impacted athletes’ risk of injury upon resumption of activities. Purpose: To describe and compare the rate, timing, mechanism, and severity of injuries among collegiate athletes across multiple sports in the Pac-12 Conference before and after the COVID-19 pandemic–associated hiatus of intercollegiate athletic activities. Study Design: Descriptive epidemiology study. Methods: Descriptive and injury data among intercollegiate athletes from both the season before the hiatus and the season after the hiatus were acquired from the Pac-12 Health Analytics Program database. Injury elements (timing of injury onset, injury severity, mechanism, recurrence, outcome, need for procedural intervention, and event segment during which the injury took place) were compared by time using the chi-square test and a multivariate logistic regression model. Subgroup analyses were performed on knee and shoulder injuries among athletes participating in sports with traditionally high rates of knee and shoulder injuries. Results: A total of 12,319 sports-related injuries across 23 sports were identified, with 7869 pre-hiatus injuries and 4450 post-hiatus injuries. There was no difference in the overall incidence of injury between the pre-hiatus and post-hiatus seasons. However, the proportion of noncontact injuries was higher in the post-hiatus season for football, baseball, and softball players, and the proportion of nonacute injuries in the post-hiatus season was higher among football, basketball, and rowing athletes. Finally, the overall proportion of injuries sustained by football players in the final 25% of competition or practice was higher in the post-hiatus season. Conclusion: Athletes competing in the post-hiatus season were observed to have higher rates of noncontact injuries and injuries sustained in the final 25% of competition. This study demonstrates that the COVID-19 pandemic has had varied effects on athletes from different sports, suggesting that many factors must be considered when designing return-to-sports programs for athletes after an extended absence from organized training.
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