Concussion-Associated Gene Variant COMT rs4680 Is Associated With Elite Rugby Athlete Status

OBJECTIVE

Concussions are common match injuries in elite rugby, and reports exist of reduced cognitive function and long-term health consequences that can interrupt or end a playing career and produce continued ill health. The aim of this study was to investigate the association between elite rugby status and 8 concussion-associated risk polymorphisms. We hypothesized that concussion-associated risk genotypes and alleles would be underrepresented in elite rugby athletes compared with nonathletes.

DESIGN

A case-control genetic association study.

SETTING

Institutional (university).

PARTICIPANTS

Elite White male rugby athletes [n = 668, mean (SD) height 1.85 (0.07) m, mass 102 (12) kg, and age 29 (7) years] and 1015 nonathlete White men and women (48% men).

INTERVENTIONS

Genotype was the independent variable, obtained by PCR of genomic DNA using TaqMan probes.

MAIN OUTCOME MEASURE

Elite athlete status with groups compared using χ 2 and odds ratio (OR).

RESULTS

The COMT rs4680 Met/Met (AA) genotype, Met allele possession, and Met allele frequency were lower in rugby athletes (24.8%, 74.6%, and 49.7%, respectively) than nonathletes (30.2%, 77.6%, and 54.0%; P < 0.05). The Val/Val (GG) genotype was more common in elite rugby athletes than nonathletes (OR 1.39, 95% confidence interval 1.04-1.86). No other polymorphism was associated with elite athlete status.

CONCLUSIONS

Elite rugby athlete status is associated with COMT rs4680 genotype that, acting pleiotropically, could affect stress resilience and behavioral traits during competition, concussion risk, and/or recovery from concussion. Consequently, assessing COMT rs4680 genotype might aid future individualized management of concussion risk among athletes.

The PPARGC1A Gly482Ser polymorphism is associated with elite long-distance running performance

Success in long-distance running relies on multiple factors including oxygen utilisation and lactate metabolism, and genetic associations with athlete status suggest elite competitors are heritably predisposed to superior performance. The Gly allele of the PPARGC1A Gly482Ser rs8192678 polymorphism has been associated with endurance athlete status and favourable aerobic training adaptations. However, the association of this polymorphism with performance amongst long-distance runners remains unclear. Accordingly, this study investigated whether rs8192678 was associated with elite status and competitive performance of long-distance runners. Genomic DNA from 656 Caucasian participants including 288 long-distance runners (201 men, 87 women) and 368 non-athletes (285 men, 83 women) was analysed. Medians of the 10 best UK times (Top10) for 10 km, half-marathon and marathon races were calculated, with all included athletes having personal best (PB) performances within 20% of Top10 (this study's definition of "elite"). Genotype and allele frequencies were compared between athletes and non-athletes, and athlete PB compared between genotypes. There were no differences in genotype frequency between athletes and non-athletes, but athlete Ser allele carriers were 2.5% faster than Gly/Gly homozygotes (p = 0.030). This study demonstrates that performance differences between elite long-distance runners are associated with rs8192678 genotype, with the Ser allele appearing to enhance performance.

Collagen Gene Polymorphisms Previously Associated with Resistance to Soft-Tissue Injury Are More Common in Competitive Runners Than Nonathletes

ABSTRACT

Dines, HR, Nixon, J, Lockey, SJ, Herbert, AJ, Kipps, C, Pedlar, CR, Day, SH, Heffernan, SM, Antrobus, MR, Brazier, J, Erskine, RM, Stebbings, GK, Hall, ECR, and Williams, AG. Collagen gene polymorphisms previously associated with resistance to soft-tissue injury are more common in competitive runners than nonathletes. J Strength Cond Res 37(4): 799-805, 2023-Single-nucleotide polymorphisms (SNPs) of collagen genes have been associated with soft-tissue injury and running performance. However, their combined contribution to running performance is unknown. We investigated the association of 2 collagen gene SNPs with athlete status and performance in 1,429 Caucasian subjects, including 597 competitive runners (354 men and 243 women) and 832 nonathletes (490 men and 342 women). Genotyping for COL1A1 rs1800012 (C > A) and COL5A1 rs12722 (C > T) SNPs was performed by a real-time polymerase chain reaction. The numbers of "injury-resistant" alleles from each SNP, based on previous literature (rs1800012 A allele and rs12722 C allele), were combined as an injury-resistance score (RScore, 0-4; higher scores indicate injury resistance). Genotype frequencies, individually and combined as an RScore, were compared between cohorts and investigated for associations with performance using official race times. Runners had 1.34 times greater odds of being rs12722 CC homozygotes than nonathletes (19.7% vs. 15.5%, p = 0.020) with no difference in the rs1800012 genotype distribution ( p = 0.659). Fewer runners had an RScore 0 of (18.5% vs. 24.7%) and more had an RScore of 4 (0.6% vs. 0.3%) than nonathletes ( p < 0.001). Competitive performance was not associated with the COL1A1 genotype ( p = 0.933), COL5A1 genotype ( p = 0.613), or RScore ( p = 0.477). Although not associated directly with running performance among competitive runners, a higher combined frequency of injury-resistant COL1A1 rs1800012 A and COL5A1 rs12722 C alleles in competitive runners than nonathletes suggests these SNPs may be advantageous through a mechanism that supports, but does not directly enhance, running performance.

Gene variants previously associated with reduced soft-tissue injury risk: Part 2 - Polygenic associations with elite status in Rugby

Part 1 of this genetic association series highlighted several genetic variants independently associated with elite status in rugby. However, it is highly likely that the genetic influence on elite status is polygenic due to the interaction of multiple genes. Therefore, the aim of the present study was to investigate whether polygenic profiles of elite rugby athletes differed from non-athletes utilising 13 genetic polymorphisms previously associated with tendon/ligament injury. Total genotype score (TGS) was calculated and multifactor dimensionality reduction (MDR) was used to calculate SNP-SNP epistasis interactions. Based on our elite rugby data from Part 1, mean TGS was significantly higher in elite rugby athletes (52.1 ± 10.7) than non-athletes (48.7 ± 10.8). There were more elite rugby athletes (54%) within the upper TGS quartile, and fewer (46%) within the lower quartile, compared to non-athletes (31% and 69%, respectively; P = 5·10^-5), and the TGS was able to distinguish between elite rugby athletes and non-athletes (area under the curve = 0.59; 95% confidence interval 0.55-0.63; P = 9·10^-7). Furthermore, MDR identified a three-SNP model of COL5A1 rs12722, COL5A1 rs3196378 and MIR608 rs4919510 that was best able to predict elite athlete status, with a greater frequency of the CC-CC-CC genotype combination in elite rugby athletes (9.8%) than non-athletes (5.3%). We propose that elite rugby athletes possess "preferable" musculoskeletal soft-tissue injury-associated polygenic profiles that have helped them achieve success in the high injury risk environment of rugby. These data may, in future, have implications for the individual management of musculoskeletal soft-tissue injury.Highlights Elite rugby athletes have preferable polygenic profiles to non-athletes in terms of genetic variants previously associated with musculoskeletal soft-tissue injury.The total genotype score was able to distinguish between elite rugby athletes and non-athletes.COL5A1 rs12722, COL5A1 rs3196378 and MIR608 rs4919510 produced the best model for predicting elite athlete status.We propose that elite rugby athletes may have an inherited advantage to achieving elite status due to an increased resistance to soft-tissue injury.

Concussion-Associated Polygenic Profiles of Elite Male Rugby Athletes

Due to the high-velocity collision-based nature of elite rugby league and union, the risk of sustaining a concussion is high. Occurrence of and outcomes following a concussion are probably affected by the interaction of multiple genes in a polygenic manner. This study investigated whether suspected concussion-associated polygenic profiles of elite rugby athletes differed from non-athletes and between rugby union forwards and backs. We hypothesised that a total genotype score (TGS) using eight concussion-associated polymorphisms would be higher in elite rugby athletes than non-athletes, indicating selection for protection against incurring or suffering prolonged effects of, concussion in the relatively high-risk environment of competitive rugby. In addition, multifactor dimensionality reduction was used to identify genetic interactions. Contrary to our hypothesis, TGS did not differ between elite rugby athletes and non-athletes (p ≥ 0.065), nor between rugby union forwards and backs (p = 0.668). Accordingly, the TGS could not discriminate between elite rugby athletes and non-athletes (AUC ~0.5), suggesting that, for the eight polymorphisms investigated, elite rugby athletes do not have a more ‘preferable’ concussion-associated polygenic profile than non-athletes. However, the COMT (rs4680) and MAPT (rs10445337) GC allele combination was more common in rugby athletes (31.7%; p < 0.001) and rugby union athletes (31.8%; p < 0.001) than non-athletes (24.5%). Our results thus suggest a genetic interaction between COMT (rs4680) and MAPT (rs10445337) assists rugby athletes in achieving elite status. These findings need exploration vis-à-vis sport-related concussion injury data and could have implications for the management of inter-individual differences in concussion risk.

Gene Variants Previously Associated with Reduced Soft Tissue Injury Risk: Part 1 - Independent Associations with Elite Status in Rugby

AbstractThere is growing evidence of genetic contributions to tendon and ligament pathologies. Given the high incidence and severity of tendon and ligament injuries in elite rugby, we studied whether 13 gene polymorphisms previously associated with tendon/ligament injury were associated with elite athlete status. Participants from the RugbyGene project were 663 elite Caucasian male rugby athletes (RA) (mean (standard deviation) height 1.85 (0.07) m, mass 101 (12) kg, age 29 (7) yr), including 558 rugby union athletes (RU) and 105 rugby league athletes. Non-athletes (NA) were 909 Caucasian men and women (56% female; height 1.70 (0.10) m, mass 72 (13) kg, age 41 (23) yr). Genotypes were determined using TaqMan probes and groups compared using Χ² and odds ratio (OR). COLGALT1 rs8090 AA genotype was more frequent in RA (27%) than NA (23%; P = 0.006). COL3A1 rs1800255 A allele was more frequent in RA (26%) than NA (23%) due to a greater frequency of GA genotype (39% vs 33%). For MIR608 rs4919510, RA had 1.7 times the odds of carrying the CC genotype compared to NA. MMP3 rs591058 TT genotype was less common in RA (25.1%) than NA (31.2%; P < 0.04). For NID1 rs4660148, RA had 1.6 times the odds of carrying the TT genotype compared to NA. It appears that elite rugby athletes have an inherited advantage that contributes to their elite status, possibly via resistance to soft tissue injury. These data may, in future, assist personalized management of injury risk amongst athletes.

Bone mineral density in high-level endurance runners: Part B-genotype-dependent characteristics

Purpose

Inter-individual variability in bone mineral density (BMD) exists within and between endurance runners and non-athletes, probably in part due to differing genetic profiles. Certainty is lacking, however, regarding which genetic variants may contribute to BMD in endurance runners and if specific genotypes are sensitive to environmental factors, such as mechanical loading via training.

Method

Ten single-nucleotide polymorphisms (SNPs) were identified from previous genome-wide and/or candidate gene association studies that have a functional effect on bone physiology. The aims of this study were to investigate (1) associations between genotype at those 10 SNPs and bone phenotypes in high-level endurance runners, and (2) interactions between genotype and athlete status on bone phenotypes.

Results

Female runners with P2RX7 rs3751143 AA genotype had 4% higher total-body BMD and 5% higher leg BMD than AC + CC genotypes. Male runners with WNT16 rs3801387 AA genotype had 14% lower lumbar spine BMD than AA genotype non-athletes, whilst AG + GG genotype runners also had 5% higher leg BMD than AG + GG genotype non-athletes.

Conclusion

We report novel associations between P2RX7 rs3751143 genotype and BMD in female runners, whilst differences in BMD between male runners and non-athletes with the same WNT16 rs3801387 genotype existed, highlighting a potential genetic interaction with factors common in endurance runners, such as high levels of mechanical loading. These findings contribute to our knowledge of the genetic associations with BMD and improve our understanding of why some runners have lower BMD than others.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00421-021-04789-z.

Bone mineral density in high-level endurance runners: part A-site-specific characteristics

PURPOSE

Physical activity, particularly mechanical loading that results in high-peak force and is multi-directional in nature, increases bone mineral density (BMD). In athletes such as endurance runners, this association is more complex due to other factors such as low energy availability and menstrual dysfunction. Moreover, many studies of athletes have used small sample sizes and/or athletes of varying abilities, making it difficult to compare BMD phenotypes between studies.

METHOD

The primary aim of this study was to compare dual-energy X-ray absorptiometry (DXA) derived bone phenotypes of high-level endurance runners (58 women and 45 men) to non-athletes (60 women and 52 men). Our secondary aim was to examine the influence of menstrual irregularities and sporting activity completed during childhood on these bone phenotypes.

RESULTS

Female runners had higher leg (4%) but not total body or lumbar spine BMD than female non-athletes. Male runners had lower lumbar spine (9%) but similar total and leg BMD compared to male non-athletes, suggesting that high levels of site-specific mechanical loading was advantageous for BMD in females only and a potential presence of reduced energy availability in males. Menstrual status in females and the number of sports completed in childhood in males and females had no influence on bone phenotypes within the runners.

CONCLUSION

Given the large variability in BMD in runners and non-athletes, other factors such as variation in genetic make-up alongside mechanical loading probably influence BMD across the adult lifespan.

Genetic Factors That Could Affect Concussion Risk in Elite Rugby

Elite rugby league and union have some of the highest reported rates of concussion (mild traumatic brain injury) in professional sport due in part to their full-contact high-velocity collision-based nature. Currently, concussions are the most commonly reported match injury during the tackle for both the ball carrier and the tackler (8-28 concussions per 1000 player match hours) and reports exist of reduced cognitive function and long-term health consequences that can end a playing career and produce continued ill health. Concussion is a complex phenotype, influenced by environmental factors and an individual's genetic predisposition. This article reviews concussion incidence within elite rugby and addresses the biomechanics and pathophysiology of concussion and how genetic predisposition may influence incidence, severity and outcome. Associations have been reported between a variety of genetic variants and traumatic brain injury. However, little effort has been devoted to the study of genetic associations with concussion within elite rugby players. Due to a growing understanding of the molecular characteristics underpinning the pathophysiology of concussion, investigating genetic variation within elite rugby is a viable and worthy proposition. Therefore, we propose from this review that several genetic variants within or near candidate genes of interest, namely APOE, MAPT, IL6R, COMT, SLC6A4, 5-HTTLPR, DRD2, DRD4, ANKK1, BDNF and GRIN2A, warrant further study within elite rugby and other sports involving high-velocity collisions.

The interactions of physical activity, exercise and genetics and their associations with bone mineral density: implications for injury risk in elite athletes

Low bone mineral density (BMD) is established as a primary predictor of osteoporotic risk and can also have substantial implications for athlete health and injury risk in the elite sporting environment. BMD is a highly multi-factorial phenotype influenced by diet, hormonal characteristics and physical activity. The interrelationships between such factors, and a strong genetic component, suggested to be around 50-85% at various anatomical sites, determine skeletal health throughout life. Genome-wide association studies and case-control designs have revealed many loci associated with variation in BMD. However, a number of the candidate genes identified at these loci have no known associated biological function or have yet to be replicated in subsequent investigations. Furthermore, few investigations have considered gene-environment interactions-in particular, whether specific genes may be sensitive to mechanical loading from physical activity and the outcome of such an interaction for BMD and potential injury risk. Therefore, this review considers the importance of physical activity on BMD, genetic associations with BMD and how subsequent investigation requires consideration of the interaction between these determinants. Future research using well-defined independent cohorts such as elite athletes, who experience much greater mechanical stress than most, to study such phenotypes, can provide a greater understanding of these factors as well as the biological underpinnings of such a physiologically "extreme" population. Subsequently, modification of training, exercise or rehabilitation programmes based on genetic characteristics could have substantial implications in both the sporting and public health domains once the fundamental research has been conducted successfully.

No association between ACTN3 R577X and ACE I/D polymorphisms and endurance running times in 698 Caucasian athletes

BACKGROUND

Studies investigating associations between ACTN3 R577X and ACE I/D genotypes and endurance athletic status have been limited by small sample sizes from mixed sport disciplines and lack quantitative measures of performance.

AIM

To examine the association between ACTN3 R577X and ACE I/D genotypes and best personal running times in a large homogeneous cohort of endurance runners.

METHODS

We collected a total of 1064 personal best 1500, 3000, 5000 m and marathon running times of 698 male and female Caucasian endurance athletes from six countries (Australia, Greece, Italy, Poland, Russia and UK). Athletes were genotyped for ACTN3 R577X and ACE ID variants.

RESULTS

There was no association between ACTN3 R577X or ACE I/D genotype and running performance at any distance in men or women. Mean (SD) marathon times (in s) were for men: ACTN3 RR 9149 (593), RX 9221 (582), XX 9129 (582) p = 0.94; ACE DD 9182 (665), ID 9214 (549), II 9155 (492) p = 0.85; for women: ACTN3 RR 10796 (818), RX 10667 (695), XX 10675 (553) p = 0.36; ACE DD 10604 (561), ID 10766 (740), II 10771 (708) p = 0.21. Furthermore, there were no associations between these variants and running time for any distance in a sub-analysis of athletes with personal records within 20% of world records.

CONCLUSIONS

Thus, consistent with most case-control studies, this multi-cohort quantitative analysis demonstrates it is unlikely that ACTN3 XX genotype provides an advantage in competitive endurance running performance. For ACE II genotype, some prior studies show an association but others do not. Our data indicate it is also unlikely that ACE II genotype provides an advantage in endurance running.

COL5A1 gene variants previously associated with reduced soft tissue injury risk are associated with elite athlete status in rugby

Background

Two common single nucleotide polymorphisms within the COL5A1 gene (SNPs; rs12722 C/T and rs3196378 C/A) have previously been associated with tendon and ligament pathologies. Given the high incidence of tendon and ligament injuries in elite rugby athletes, we hypothesised that both SNPs would be associated with career success.

Results

In 1105 participants (RugbyGene project), comprising 460 elite rugby union (RU), 88 elite rugby league athletes and 565 non-athlete controls, DNA was collected and genotyped for the COL5A1 rs12722 and rs3196378 variants using real-time PCR. For rs12722, the injury-protective CC genotype and C allele were more common in all athletes (21% and 47%, respectively) and RU athletes (22% and 48%) than in controls (16% and 41%, P ≤ 0.01). For rs3196378, the CC genotype and C allele were overrepresented in all athletes (23% and 48%) and RU athletes (24% and 49%) compared with controls (16% and 41%, P ≤ 0.02). The CC genotype in particular was overrepresented in the back and centres (24%) compared with controls, with more than twice the odds (OR = 2.25, P = 0.006) of possessing the injury-protective CC genotype. Furthermore, when considering both SNPs simultaneously, the CC–CC SNP-SNP combination and C–C inferred allele combination were higher in all the athlete groups (≥18% and ≥43%) compared with controls (13% and 40%; P = 0.01). However, no genotype differences were identified for either SNP when RU playing positions were compared directly with each other.

Conclusion

It appears that the C alleles, CC genotypes and resulting combinations of both rs12722 and rs3196378 are beneficial for rugby athletes to achieve elite status and carriage of these variants may impart an inherited resistance against soft tissue injury, despite exposure to the high-risk environment of elite rugby. These data have implications for the management of inter-individual differences in injury risk amongst elite athletes.

Polymorphisms in PTK2 are associated with skeletal muscle specific force: an independent replication study

PURPOSE

The aim of the study was to investigate two single nucleotide polymorphisms (SNP) in PTK2 for associations with human muscle strength phenotypes in healthy men.

METHODS

Measurement of maximal isometric voluntary knee extension (MVC_KE) torque, net MVC_KE torque and vastus lateralis (VL) specific force, using established techniques, was completed on 120 Caucasian men (age = 20.6 ± 2.3 year; height = 1.79 ± 0.06 m; mass = 75.0 ± 10.0 kg; mean ± SD). All participants provided either a blood (n = 96) or buccal cell sample, from which DNA was isolated and genotyped for the PTK2 rs7843014 A/C and rs7460 A/T SNPs using real-time polymerase chain reaction.

RESULTS

Genotype frequencies for both SNPs were in Hardy-Weinberg equilibrium (X ² ≤ 1.661, P ≥ 0.436). VL specific force was 8.3% higher in rs7843014 AA homozygotes than C-allele carriers (P = 0.017) and 5.4% higher in rs7460 AA homozygotes than T-allele carriers (P = 0.029). No associations between either SNP and net MVC_KE torque (P ≥ 0.094) or peak MVC_KE torque (P ≥ 0.107) were observed.

CONCLUSIONS

These findings identify a genetic contribution to the inter-individual variability within muscle specific force and provides the first independent replication, in a larger Caucasian cohort, of an association between these PTK2 SNPs and muscle specific force, thus extending our understanding of the influence of genetic variation on the intrinsic strength of muscle.

Fat mass and obesity associated (FTO) gene influences skeletal muscle phenotypes in non-resistance trained males and elite rugby playing position

Background

FTO gene variants have been associated with obesity phenotypes in sedentary and obese populations, but rarely with skeletal muscle and elite athlete phenotypes.

Methods

In 1089 participants, comprising 530 elite rugby athletes and 559 non-athletes, DNA was collected and genotyped for the FTO rs9939609 variant using real-time PCR. In a subgroup of non-resistance trained individuals (NT; n = 120), we also assessed structural and functional skeletal muscle phenotypes using dual energy x-ray absorptiometry, ultrasound and isokinetic dynamometry. In a subgroup of rugby athletes (n = 77), we assessed muscle power during a countermovement jump.

Results

In NT, TT genotype and T allele carriers had greater total body (4.8% and 4.1%) and total appendicular lean mass (LM; 3.0% and 2.1%) compared to AA genotype, with greater arm LM (0.8%) in T allele carriers and leg LM (2.1%) for TT, compared to AA genotype. Furthermore, the T allele was more common (94%) in selected elite rugby union athletes (back three and centre players) who are most reliant on LM rather than total body mass for success, compared to other rugby athletes (82%; P = 0.01, OR = 3.34) and controls (84%; P = 0.03, OR = 2.88). Accordingly, these athletes had greater peak power relative to body mass than other rugby athletes (14%; P = 2 x 10^-6).

Conclusion

Collectively, these results suggest that the T allele is associated with increased LM and elite athletic success. This has implications for athletic populations, as well as conditions characterised by low LM such as sarcopenia and cachexia.

Genetic Testing for Sports Performance, Responses to Training and Injury Risk: Practical and Ethical Considerations

This paper addresses practical and ethical considerations regarding genetic tests to predict performance and/or risk of exercise-related injury or illness. Various people might wish to conduct sport-related genetic tests for a variety of reasons. For example, an individual might seek personal genetic information to help guide their own sport participation. A sports coach might wish to test young athletes to aid team selection or individualize training. A physician might want to predict the risk of injury or illness in athletes and advise regarding selection or preventative measures. An insurance company might seek to estimate the risk of career-threatening injury for athletes based partly on genetic information. Whilst this information is, in part, encoded in our DNA sequence, the available tests allow generally only a poor prediction of the aforementioned variables. In other words, the current genetic tests and analysis methods are not powerful enough to inform important decisions in sport to a substantial degree. It is particularly disappointing that more than half of the commercially available genetic tests related to exercise and sport do not appear to identify publicly the genetic variants they assess, making scrutiny by academic scholars and consumers (or their representatives) impossible. There are also challenging ethical issues to consider. For example, the imposition of genetic tests on individuals (especially young people) by third parties is potentially susceptible to abuse. Scientists and practitioners should understand the limitations of the tests currently available, the ethical concerns and the importance of counselling before and after testing so that they are only used in a responsible manner.

Association of ACTN3 R577X but not ACE I/D gene variants with elite rugby union player status and playing position

We aimed to quantify the ACE I/D and ACTN3 R577X (rs1815739) genetic variants in elite rugby athletes (rugby union and league) and compare genotype frequencies to controls and between playing positions. The rugby athlete cohort consisted of 507 Caucasian men, including 431 rugby union athletes that for some analyses were divided into backs and forwards and into specific positional groups: front five, back row, half backs, centers, and back three. Controls were 710 Caucasian men and women. Real-time PCR of genomic DNA was used to determine genotypes using TaqMan probes and groups were compared using χ² and odds ratio (OR) statistics. Correction of P values for multiple comparisons was according to Benjamini-Hochberg. There was no difference in ACE I/D genotype between groups. ACTN3 XX genotype tended to be underrepresented in rugby union backs (15.7%) compared with forwards (24.8%, P = 0.06). Interestingly, the 69 back three players (wings and full backs) in rugby union included only six XX genotype individuals (8.7%), with the R allele more common in the back three (68.8%) than controls (58.0%; χ² = 6.672, P = 0.04; OR = 1.60) and forwards (47.5%; χ² = 11.768, P = 0.01; OR = 2.00). Association of ACTN3 R577X with playing position in elite rugby union athletes suggests inherited fatigue resistance is more prevalent in forwards, while inherited sprint ability is more prevalent in backs, especially wings and full backs. These results also demonstrate the advantage of focusing genetic studies on a large cohort within a single sport, especially when intrasport positional differences exist, instead of combining several sports with varied demands and athlete characteristics.

Genomics in rugby union: A review and future prospects

This article introduces some aspects of sports genomics in a rugby union context, considers the rugby-specific genetic data in the published literature and outlines the next research steps required if the potential applications of genetic technology in rugby union, also identified here, are to become possible. A substantial proportion of the inter-individual variation for many traits related to rugby performance, including strength, short-term muscle power, VO2 max, injury susceptibility and the likelihood of being an elite athlete is inherited and can be investigated using molecular genetic techniques. In sports genomics, significant efforts have been made in recent years to develop large DNA biobanks of elite athletes for detailed exploration of the heritable bases of those traits. However, little effort has been devoted to the study of rugby athletes, and most of the little research that has focused on rugby was conducted with small cohorts of non-elite players. With steadily growing knowledge of the molecular mechanisms underpinning complex performance traits and the aetiology of injury, investigating sports genomics in the context of rugby is now a viable proposition and a worthwhile endeavour. The RugbyGene project we describe briefly in this article is a multi-institutional research collaboration in rugby union that will perform molecular genetic analyses of varying complexity. Genetic tests could become useful tools for rugby practitioners in the future and provide complementary and additional information to that provided by the non-genetic tests currently used.

Variability and distribution of muscle strength and its determinants in humans

INTRODUCTION

Inter-individual variability in measurements of muscle strength and its determinants was identified to: (1) produce a normative data set describing the normal range and (2) determine whether some measurements are more informative than others when evaluating inter-individual differences.

METHODS

Functional and morphological characteristics of the vastus lateralis were measured in 73 healthy, untrained adult men.

RESULTS

Inter-individual variability (coefficient of variation) was greater for isometric maximal voluntary contraction (MVC) torque (18.9%) compared with fascicle force (14.6%; P=0.025) and physiological cross-sectional area (PCSA; 17.2%) compared with anatomical cross-sectional area (ACSA, 13.0%; P<0.0005). The relationship between ACSA and isometric MVC torque (r(2)  =0.56) was weaker than that between PCSA and fascicle force (r(2)  =0.68).

CONCLUSIONS

These results provide a normative data set on inter-individual variability in a variety of muscle strength-related measurements and illustrate the benefit of using more stringent measures of muscle properties. Muscle Nerve 49: 879-886, 2014.

Variation in the uncoupling protein 2 and 3 genes and human performance

Uncoupling proteins 2 and 3 (UCP2 and UCP3) may negatively regulate mitochondrial ATP synthesis and, through this, influence human physical performance. However, human data relating to both these issues remain sparse. Examining the association of common variants in the UCP3/2 locus with performance phenotypes offers one means of investigation. The efficiency of skeletal muscle contraction, delta efficiency (DE), was assessed by cycle ergometry in 85 young, healthy, sedentary adults both before and after a period of endurance training. Of these, 58 were successfully genotyped for the UCP3-55C>T (rs1800849) and 61 for the UCP2-866G>A (rs659366) variant. At baseline, UCP genotype was unrelated to any physical characteristic, including DE. However, the UCP2-866G>A variant was independently and strongly associated with the DE response to physical training, with UCP2-866A allele carriers exhibiting a greater increase in DE with training (absolute change in DE of -0.2 ± 3.6% vs. 1.7 ± 2.8% vs. 2.3 ± 3.7% for GG vs. GA vs. AA, respectively; P = 0.02 for A allele carriers vs. GG homozygotes). In multivariate analysis, there was a significant interaction between UCP2-866G>A and UCP3-55C>T genotypes in determining changes in DE (adjusted R(2) = 0.137; P value for interaction = 0.003), which was independent of the effect of either single polymorphism or baseline characteristics. In conclusion, common genetic variation at the UCP3/2 gene locus is associated with training-related improvements in DE, an index of skeletal muscle performance. Such effects may be mediated through differences in the coupling of mitochondrial energy transduction in human skeletal muscle, but further mechanistic studies are required to delineate this potential role.

Genetics of muscle strength and power: polygenic profile similarity limits skeletal muscle performance

Environmental and genetic factors influence muscle function, resulting in large variations in phenotype between individuals. Multiple genetic variants (polygenic in nature) are thought to influence exercise-related phenotypes, yet how the relevant polymorphisms combine to influence muscular strength in individuals and populations is unclear. In this analysis, 22 genetic polymorphisms were identified in the literature that have been associated with muscular strength and power phenotypes. Using typical genotype frequencies, the probability of any given individual possessing an "optimal" polygenic profile was calculated as 0.0003% for the world population. Future identification of additional polymorphisms associated with muscular strength phenotypes would most likely reduce that probability even further. To examine the genetic potential for muscular strength within a human population, a "total genotype score" was generated for each individual within a hypothetical population of one million. The population expressed high similarity in polygenic profile with no individual differing by more than seven genotypes from a typical profile. Therefore, skeletal muscle strength potential within humans appears to be limited by polygenic profile similarity. Future research should aim to replicate more genotype-phenotype associations for muscular strength, because only five common genetic polymorphisms identified to date have positive replicated findings.

Protocols of in vitro protein covalent binding studies in liver

Xenobiotics, including therapeutic agents, can produce a variety of beneficial, as well as adverse, effects in mammals. One potential source of drug-mediated toxicity stems from metabolic activation of the parent compound, typically catalyzed by one or more members of the cytochrome P450 family of enzymes. The resulting electrophile, if not quenched by low molecular weight endogenous nucleophiles, can form covalent adducts to cellular proteins, potentially resulting in enzyme inactivation, cell death, or formation of an immunogenic species. The toxicological consequences of exposure to such reactive intermediates range from mild inflammation to organ failure, anaphylaxis, and death. At Merck Research Laboratories, the potential of drug candidates to bind covalently to proteins is evaluated at the lead optimization stage of drug discovery by incubating a radiolabeled analog of the compound in question with liver microsomal preparations (under oxidative conditions) or whole cells (full cellular metabolic capability), typically derived from rat and human liver. A semi-automated method based on the Brandel Harvester technique then is used to measure the formation of covalent adducts of the test compound to liver proteins. This assay is viewed as an important component of drug discovery programs, since the findings are employed to guide specific efforts to abrogate bioactivation issues through informed structural modification of lead compounds.

The effect of crank inertial load on the physiological and biomechanical responses of trained cyclists

The existing literature suggests that crank inertial load has little effect on the responses of untrained cyclists. However, it would be useful to be aware of any possible effect in the trained population, particularly considering the many laboratory-based studies that are conducted using relatively low-inertia ergometers. Ten competitive cyclists (mean VO(2max) = 62.7 ml x kg(-1) x min(-1), s = 6.1) attended the human performance laboratories at the University of Wolverhampton. Each cyclist completed two 7-min trials, at two separate inertial loads, in a counterbalanced order. The inertial loads used were 94.2 kg x m(2) (high-inertia trial) and 2.4 kg x m(2) (low-inertia trial). Several physiological and biomechanical measures were undertaken. There were no differences between inertial loads for mean peak torque, mean minimum torque, oxygen uptake, blood lactate concentration or perceived exertion. Several measures showed intra-individual variability with blood lactate concentration and mean minimum torque, demonstrating coefficients of variation > 10%. However, the results presented here are mostly consistent with previous work in suggesting that crank inertial load has little direct effect on either physiology or propulsion biomechanics during steady-state cycling, at least when cadence is controlled.

Metabolic activation of indole-containing prostaglandin D2 receptor 1 antagonists: Impacts of glutathione trapping and glucuronide conjugation on covalent binding

Some DP1 receptor antagonists from an indole-containing series were shown to cause in vitro covalent binding to protein in rat and human liver microsomes. Glutathione trapping experiments along with in vitro labeling assays confirmed that the presence of a strong electron withdrawing group was necessary to abrogate in vitro covalent binding, leading to the discovery of MK-0524. Hepatocyte incubations and in vivo studies showed that acyl-glucuronide formation did not translate into covalent binding.

Discovery of a Potent and Selective Prostaglandin D2 Receptor Antagonist, [(3R)-4-(4-Chloro- benzyl)-7-fluoro-5-(methylsulfonyl)-1,2,3,4-tetrahydrocyclopenta[b]indol-3-yl]-acetic Acid (MK-0524)

The discovery of the potent and selective prostaglandin D2 (PGD2) receptor (DP) antagonist [(3R)-4-(4-chlorobenzyl)-7-fluoro-5-(methylsulfonyl)-1,2,3,4-tetrahydrocyclopenta[b]indol-3-yl]-acetic acid (13) is presented. Initial lead antagonists 6 and 7 were found to be potent and selective DP antagonists (DP Ki = 2.0 nM for each); however, they both suffered from poor pharmacokinetic profiles, short half-lives and high clearance rates in rats. Rat bile duct cannulation studies revealed that high concentrations of parent drug were present in the biliary fluid (Cmax = 1100 microM for 6 and 3900 microM for 7). This pharmacokinetic liability was circumvented by replacing the 7-methylsulfone substituent present in 6 and 7 with a fluorine atom resulting in antagonists with diminished propensity for biliary excretion and with superior pharmacokinetic profiles. Further optimization led to the discovery of the potent and selective DP antagonist 13.

No correlation between circulating ACE activity and $$ {\user2{V}}{\mathbf{O}}_{{{\mathbf{2}}_{{{\mathbf{max}}}} }} $$ or mechanical efficiency in women

The insertion (I) variant of the angiotensin-1 converting enzyme (ACE) I/D genetic polymorphism is associated with lower circulating and tissue ACE activity. Some studies have also suggested associations of ACE I/D genotype with endurance phenotypes. This study assessed the relationships between circulating ACE activity, ACE I/D genotype, mechanical efficiency and the maximal rate of oxygen uptake in sedentary individuals. Sixty-two untrained women were tested for mechanical efficiency during submaximal cycle ergometry (delta and gross efficiencies during exercise between 40 and 80 W) and the maximal rate of oxygen uptake during incremental treadmill running. Respiratory variables were measured using indirect calorimetry. Venous blood was obtained for direct assay of circulating ACE activity, allowing for the assessment of correlations between two continuous variables, rather than a categorical analysis of endurance phenotype by genotype alone. ACE I/D genotype was also determined, and was strongly associated with circulating ACE activity (P < 0.0005). Neither circulating ACE activity (27.4 +/- 8.4 nM His-Leu-ml(-1)) nor ACE genotype showed a statistically significant association with any of the endurance phenotypes measured. The weak correlations observed included r = -0.122 (P = 0.229) for the relationship between delta efficiency (23.9 +/- 2.5%) and circulating ACE activity and r = 0.134 (P > 0.6) for the relationship between maximal aerobic power (149.1 +/- 22.9 ml kg(-2/3) min(-1)) and circulating ACE activity. The data do not support a role for systemic ACE activity in the regulation of endurance performance in sedentary individuals, extending this observation to a large female cohort.

A semi-automated method for measuring the potential for protein covalent binding in drug discovery

INTRODUCTION

Covalent protein binding of metabolically reactive intermediates of drugs has been implicated in drug toxicity including the occurrence of idiosyncratic drug toxicity. Investigators therefore would prefer to avoid developing compounds that produce significant amounts of reactive metabolites. By incubating the radiolabeled drug of interest with liver microsomes it is possible to evaluate the propensity of a drug candidate to covalently bind to proteins.

METHODS

Here we present a semi-automated method in which a Brandel cell harvester is used to collect and wash proteins that have been incubated with radiolabeled drug. This method utilizes glass fiber filter paper to capture precipitated protein, rather than the more traditional exhaustive extraction/centrifugation approach. Using model compounds (including [14C]diclofenac, [3H]imipramine, [14C]naphthalene, and [14C]L-746530) we compare the covalent binding results obtained using this method to results generated using the traditional method and we performed cross-laboratory testing of assay reproducibility.

RESULTS

It was found that results from new method correlated highly with the traditional method (R2=0.89). The cross-laboratory testing of the method showed an average interlaboratory coefficient of variation of only 18.4%.

DISCUSSION

This method provides comparable results to the more traditional centrifugation-based method with considerable time and labor savings.

Circulating angiotensin converting enzyme activity is correlated with muscle strength

PURPOSE

The D-variant of the angiotensin-1 converting enzyme (ACE) gene is associated with higher circulating and tissue ACE activity. Some studies have suggested a similar association of genotype with muscle strength or the gain in strength in response to training. This study has assessed the relationship between circulating ACE activity, strength, and the response to training.

METHODS

Eighty-one untrained men were tested for quadriceps muscle strength, and 44 of these performed an 8-wk program of dynamic strength training of the quadriceps muscle group. Venous blood was obtained for assessment of circulating ACE activity before and after the training program. ACE genotype was also determined.

RESULTS

At baseline, circulating ACE activity was significantly correlated with isometric (r = 0.25-0.29, P < 0.02) and isokinetic (r = 0.38, P < 0.0005) quadriceps muscle strength. ACE genotype also seemed to be related to pretraining muscle strength. However, circulating ACE activity showed no significant association with the 9-14% mean increases of muscle strength in response to the training intervention. ACE genotype also showed no association with the training-induced change in muscle strength. Circulating ACE activity did not change significantly after the training program.

CONCLUSIONS

The data support a role for ACE in the regulation of human skeletal muscle strength, but do not confirm a role in altering the response to short-term training.

USE OF A BENZYLOXY-SUBSTITUTED LACTONE CYCLOOXYGENASE-2 INHIBITOR AS A SELECTIVE FLUORESCENT PROBE FOR CYP3A ACTIVITY IN PRIMARY CULTURED RAT AND HUMAN HEPATOCYTES

Previously, we have shown that the inhibition of the transporter-mediated hepatic uptake of cerivastatin (CER) by cyclosporin A (CsA) could, at least partly, explain a pharmacokinetic interaction between these drugs in humans. In the present study, we have examined the effect of CsA on the in vivo disposition of CER in rats and the in vitro uptake of [14C]CER in isolated rat hepatocytes in an attempt to evaluate the effect of inhibition of transporter-mediated hepatic uptake on the in vivo CER disposition. The steady-state plasma concentration of CER increased 1.4-fold when coadministered with CsA up to a steady-state blood concentration of 4 microM. Studies of [14C]CER uptake into isolated rat hepatocytes showed saturable transport, with the saturable portion accounting for more than 80% of the total uptake. CsA competitively inhibited the uptake of [14C]CER with a Ki of 0.3 microM. The IC50 for the uptake of [14C]CER in the absence and presence of rat plasma was 0.2 and 2.3 microM, respectively. The in vivo hepatic uptake of [14C]CER evaluated by the liver uptake index method was also inhibited by CsA in a dose-dependent manner. On the other hand, CsA did not inhibit the metabolism of [14C]CER in rat microsomes. The in vitro and in vivo correlation analysis revealed that this pharmacokinetic interaction between these drugs in rats could be quantitatively explained by the inhibition of transporter-mediated hepatic uptake. Thus, this drug-drug interaction in rats is predominantly caused by the transporter-mediated uptake process.

The acute effects of exercise and glucose ingestion on circulating angiotensin-converting enzyme in humans

Angiotensin-converting enzyme (ACE) activity has been suggested as a determinant of some exercise phenotypes via some studies that have associated the ACE gene with exercise performance, although several studies provide conflicting evidence regarding the influence of the ACE gene. The relationships between ACE phenotype (ACE activity) and various exercise parameters should also be examined. An early step in this process is to determine whether common environmental stimuli such as exercise and diet have acute effects on ACE activity. In this study, the acute effects of aerobic exercise, resistance exercise and glucose ingestion on circulating ACE activity were examined. On three separate occasions, 20 healthy adult volunteers (9 female and 11 male) performed 20 min of submaximal cycle exercise at 70-80% of maximal heart rate, four sets of ten repetitions of unilateral leg extension resistance exercise at ten-repetition maximum load, or ingested 1 g kg(-1) glucose. Circulating ACE activity was assessed for 1 h after each intervention using a modified fluorometric method. Pre-intervention ACE activity remained remarkably stable across test days (difference < or =1.8%). Furthermore, there was no significant change in circulating ACE activity following any of the interventions (difference from pre-intervention values < or =6.8% when unadjusted for plasma volume changes, < or =4.5% when adjusted for plasma volume changes). These results suggest that acute exercise and glucose ingestion interventions as used here do not affect circulating ACE activity. These findings are an early step in illuminating the relationships between ACE activity and various exercise parameters.

Bradykinin receptor gene variant and human physical performance

Accumulating evidence suggests that athletic performance is strongly influenced by genetic variation. One such locus of influence is the gene for angiotensin-I converting enzyme (ACE), which exhibits a common variant [ACE insertion (I)/deletion (D)]. ACE can drive formation of vasoconstrictor ANG II but preferentially degrades vasodilator bradykinin. The ACE I allele is associated with higher kinin activity. A common gene variant in the kinin β2 receptor (B2R) exists: the -9 as opposed to +9 allele is associated with higher receptor mRNA expression. We tested whether this variant was associated with the efficiency of muscular contraction [delta efficiency (DE)] in 115 healthy men and women, or with running distance among 81 Olympic standard track athletes. We further sought evidence of biological interaction with ACE I/D genotype. DE was highly significantly associated with B2R genotype (23.84 ± 2.41 vs. 24.25 ± 2.81 vs. 26.05 ± 2.26% for those of +9/+9 vs. +9/-9 vs. -9/-9 genotype; n = 25, 61, and 29, respectively; P = 0.0008 for ANOVA adjusted for sex). There was evidence for interaction with ACE I/D genotype, with individuals who were ACE II, with B2R -9/-9 having the highest DE at baseline. The ACE I/B2R -9 “high kinin receptor activity” haplotype was significantly associated with endurance (predominantly aerobic) event among elite athletes ( P = 0.003). These data suggest that common genetic variation in the B2R is associated with efficiency of skeletal muscle contraction and with distance event of elite track athletes and that at least part of the associations of ACE and fitness phenotypes is through elevation of kinin activity.

Bioactive constituents of the roots of Cynanchum atratum

A novel biphenylneolignan, 2,6,2',6'-tetramethoxy-4,4'-bis(2,3-epoxy-1-hydroxypropyl)biphenyl (1), and two new glycosides named atratoglaucosides A (2) and B (3), were isolated from the roots of Cynanchum atratum, and their structures were determined on the basis of chemical and spectroscopic evidence. The aglycons of 2 and 3 were identified as glaucogenin C and 7-desoxyneocynapanogenin A, a new disecopregnane. A known compound, glaucogenin C 3-O-beta-D-cymaropyranosyl-(1-->4)-alpha-L-diginopyranosyl-(1-->4)-beta-D-thevetopyranoside (4), isolated from the same source, showed a significant cytotoxic effect against 212 cells. This substance also gave a significant inhibitory effect on TNF-alpha (tumor necrosis factor-alpha) formation from the RAW 264.7 mouse macrophage-like cell line stimulated with LPS (lipopolysaccharide) and on the N9 microglial cell line stimulated with LPS/IFN-gamma (interferon-gamma).

New lignan glycosides with potent antiinflammatory effect, isolated from Justicia ciliata

Two new lignan glycosides, 4-O-[alpha-L-arabinopyranosyl-(1' "-->2' ')-beta-D-xylopyranosyl-(1' " '-->5' ')-beta-D-apiofuranosyl]diphyllin (1), named ciliatoside A (1), and 4-O-¿[beta-D-apiofuranosyl-(1' " "-->3' ")-alpha-L-arabinopyranosyl-(1' "-->2' ')][beta-D-xylopyranosyl-(1' " '-->5' ')]-beta-D-apiofuranosyl¿diphyllin (2), named ciliatoside B (2), were isolated from the whole plant of Justicia ciliata. The structures of 1 and 2 were determined by spectral and chemical methods. Compounds 1 and 2 strongly inhibited the accumulation of NO(2)(-) in lipopolysaccharide-stimulated RAW 264.7 cells in a concentration-dependent manner with IC(50) values of 27.1 +/- 1.6 and 29.4 +/- 1.4 microM, respectively.

Cytotoxic lignans of Justicia ciliata

Two new naturally occurring 1-aryl-2,3-naphthalide lignans, cilinaphthalide A (1) and cilinaphthalide B (2), and nine known compounds were isolated from the whole plant of Justicia ciliata. Their structures were established by spectral analysis, and their cytotoxic activity was evaluated against several different cell lines. The known compound, justicidin A, showed potent cytotoxic effects against T-24, CaSki, SiHa, HT-3, PLC/PRF/5, and 212 cells in vitro.

Induction of cytochrome-P450 in cryopreserved rat and human hepatocytes

Our laboratory has been routinely using suspended and cultured human hepatocytes for predicting drug metabolism and enzyme induction by drug candidates to aid drug discovery. Increasing limitation and irregular availability of human tissue has indicated the need for maximizing the use of this valuable resource. Cryopreservation of surplus hepatocytes after isolation would greatly increase the potential of this model. However, cryopreservation of hepatocytes by various methods has resulted in cells with poor metabolic activity and unacceptably low survival rates in culture. Recently, Zaleski et al. (Biochem. Pharmacol. 46 (1993) 111-116) reported that cryopreserved rat hepatocytes retained metabolic capacity similar to fresh hepatocytes when the cells were preincubated for 30 min at 37 degrees C in Krebs Ringer bicarbonate buffer prior to freezing. To further explore this methodology, both the functional capacity of the cells in culture as well as their ability to retain CYP inducibility were investigated with thawed cryopreserved hepatocytes. Although human hepatocytes were used in this study the initial work focused on rat hepatocytes as a cell model. Our results showed that while the preincubation step did not appear to effect the initial viability of cryopreserved hepatocytes, survival of the cells in culture was greatly enhanced. Plating efficiencies for nonpreincubated cryopreserved hepatocytes were decreased to approximately 15% of fresh cells after 48 h in culture. In contrast, cells that had been preincubated prior to freezing had an excellent plating efficiency (approximately 60%) and responded to classical CYP inducers dexamethasone, beta-naphthoflavone and phenobarbital in a manner indistinguishable from that of fresh hepatocytes. Experiments with human hepatocytes have also demonstrated similar results. This is the first time to our knowledge that cryopreserved hepatocytes from both rat and human have been shown to reproducibly respond to CYP inducers in culture.

Molecular flexibility profiling using NMR spectroscopy

Molecular flexibility is a factor that is not extensively studied in most pharmaceutical research efforts. When it is, the level of effort is high involving the preparation of detailed models supported by either molecular dynamics simulations and/or Nuclear Magnetic Resonance data. While these studies are both powerful and illuminating, they cannot be routinely applied in a drug discovery setting as they are time and expertise intensive. Yet there seems to be little doubt that at least in some cases, molecular flexibility plays a key role in complex formation. A simple, rapid and generally applicable flexibility profiling protocol was applied to two model systems and data describing the internal mobility of carbon atoms were obtained. The protocol utilizes the Model Free approach and NMR data to characterize the internal molecular dynamics of these compounds. The first model system consisted of fluorene and diphenylmethane where the anticipated flexibility trends were observed in the data providing a link between chemical intuition and the experimental results. Data on a second model system, which consisted of two Paclitaxel analogs, showed predictable patterns including dynamical phenyl and methyl groups and a relatively immobile taxane core. Subtle differences in the internal dynamics within the taxane core suggest that it cannot be considered as a rigid structure. Key advantages of using this approach are that no prior knowledge or supposition of dynamical features is required, the protocol can be carried out in most medicinal chemistry laboratories and the data obtained provide a common, empirically derived reference point to discuss the effects of molecular flexibility on activity.

Cryopreservation of rat and human liver slices by rapid freezing

The cryopreservation of human liver slices is a promising way to enhance the ability to test the metabolism of drug candidates. This study demonstrates the use of a novel technique for the cryopreservation of both rat and human liver slices. In this technique the slices are treated with Me2SO and sandwiched between aluminum plates separated by a thin gasket. The device is then submerged in liquid nitrogen to freeze the slices, which can then be stored until use. To thaw the slices, the apparatus is submerged in a water bath at 37 degrees C. Slices frozen and thawed in this manner were compared to those frozen in conventional cryovials. The viability of the slices was determined by incubating them in 12-well plates and measuring urea synthesis, ethoxycoumarin metabolism, and cytosolic enzyme leakage (LDH and ALT). The viability of rat slices frozen between plates approached that of fresh slices and was consistently higher than slices frozen in cryovials. Slices from two human samples gave similar results. The technique was found to work over a wide range of Me2SO concentrations (4.5 to 22% was tested) with an optimal concentration between 10 and 15%.

Ophthalmology's future in the next decade: a historical and comparative perspective

PURPOSE

To gain a historical and comparative perspective about the future of ophthalmology within the profession of medicine.

METHODS

A literature search is made of disciplines other than medicine (history, sociology, philosophy, economics, and ethics) in order to assess factors responsible for survival and healthiness of a profession. The "learned" professions (medicine, law, and theology) are assessed. Other "professional" careers valued by society (sports and classical music) are reviewed.

RESULTS

From the perspective of other disciplines, the future of ophthalmology is seen as vulnerable and fragile. Survival of professions, be they classically or economically defined, is linked to societal needs, a profession's unique commitment and ability to provide services to society, and the profession's maintenance of knowledge as well as skill-based services. Historical evidence has shown erosion of a profession's power consequent to capitalist influences, government influences, access of skills by less trained individuals, and elitist posturing by a profession. Comparative evidence has shown societal acceptance of an escalation of salaries for designated superstars, increasing roles and influence of managerial personnel, and trivialization of values other than economic ones.

CONCLUSION

Attention to historical and comparative trends by individual ophthalmologists as well as associations representing ophthalmologists is mandatory if ophthalmology as we know it is to survive within the profession of medicine.

Manipulation of knee extensor force using percutaneous electrical myostimulation during eccentric actions: effects on indices of muscle damage in humans

Percutaneous electrical myostimulation (PES) was used to manipulate the force produced by the knee extensor muscles during eccentric exercise, thereby providing a model to investigate the role of force in muscle damage. Two eccentric exercise bouts of equal work were performed by nine subjects, using fixed voltage PES at 20 Hz (to produce moderate muscle forces) and 100 Hz (to produce high muscle forces). Muscle contractility, serum creatine kinase activity (CK) and muscle soreness (MS) were evaluated before, and up to 14 days after exercise. Data are presented as means+/-SEM, and were analysed using repeated measures analysis of variance (ANOVA), t-tests and Wilcoxon tests. Peak forces were higher during the 100 Hz bout than the 20 Hz bout for repetitions 1 (472+/-60 vs 237+/-23 Newtons), 10 (381+/-26 vs 233+/-26 Newtons), 20 (310+/-24 vs 218+/-24 Newtons), all p < 0.01, t-test and 30 (297+/-27 vs 204+/-21 Newtons), p < 0.05, t-test. Following the 100 Hz bout, maximum voluntary contractile force (MVC) was lower (p<0.01, ANOVA), and CK was higher (p<0.0001, ANOVA) than after the 20 Hz bout. Subjects also reported greater MS on days 2 to 6 (p<0.05, Wilcoxon test) following the 100 Hz bout. Despite a decline in the stimulated 20:100 Hz tetanic force ratio after each bout (p<0.01, ANOVA) there was no difference between bouts (p>0.05, ANOVA). The higher rise in CK and MS after the 100 Hz bout, together with the greater deficit in MVC, suggest that in humans, muscle force is a contributing factor to muscle injury during eccentric actions.

Electromyogram activity and mean power frequency in exercise-damaged human muscle

Eight volunteers performed two bouts of 50 voluntary maximal eccentric contractions of the knee extensors of one leg 3 weeks apart. During maximal voluntary isometric contractions performed at intervals after each bout, electromyogram (EMG) mean power frequency declined after bout one (P < 0.01 Duncan's test), whereas integrated EMG did not change after either bout. These results suggest that unaccustomed eccentric contractions produce a temporary reduction in mean muscle activation frequency during subsequent maximal isometric contractions.

The effect of severe eccentric exercise-induced muscle damage on plasma elastase, glutamine and zinc concentrations

The aim of this study was to determine if severe exercise-induced muscle damage alters the plasma concentrations of glutamine and zinc. Changes in plasma concentrations of glutamine, zinc and polymorphonuclear elastase (an index of phagocytic cell activation) were examined for up to 10 days following eccentric exercise of the knee extensors of one leg in eight untrained subjects. The exercise bout consisted of 20 repetitions of electrically stimulated eccentric muscle actions on an isokinetic dynamometer. Subjects experienced severe muscle soreness and large increases in plasma creatine kinase activity indicative of muscle fibre damage. Peak soreness occurred at 2 days post-exercise and peak creatine kinase activity [21714 (6416) U x l(-1) mean (SEM)] occurred at 3 days post-exercise (P < 0.01 compared with pre-exercise). Plasma elastase concentration was increased at 3 days post-exercise compared with pre-exercise (P < 0.05), and is presumably indicative of ongoing phagocytic leucocyte infiltration and activation in the damaged muscles. There were no significant changes in plasma zinc and glutamine concentrations in the days following eccentric exercise. We conclude that exercise-induced muscle damage does not produce changes in plasma glutamine or zinc concentrations despite evidence of phagocytic neutrophil activation.