Attending a social event and consuming alcohol is associated with changes in serum microRNA: a before and after study in healthy adults.

PURPOSE: Circulating microRNAs represent a reservoir for biomarker discovery. Our objective was to profile the change in human circulating microRNA associated with recreational use of alcohol at a social event. MATERIAL AND METHODS: Blood was collected from healthy volunteers (N = 16) before and after recreational consumption of alcohol (ethanol). Biochemistry, hematology and ethanol measurements were performed. The change in the serum small RNA fraction was quantified by RNA sequencing. RESULTS: Blood ethanol was undetectable at study entry in all subjects [<10 mg/dL]. After consuming alcohol the median concentration was 89 mg/dL [IQR: 71-138. Min-max 20-175]. There were no changes in biochemistry and hematology parameters. Serum RNA sequencing identified 1371 small RNA species (1305 microRNAs). There were significant increases [adjusted p-value <0.05, fold increase 2 or more] in 265 microRNAs, around a fifth of the total [median fold increase 2.3 [IQR: 2.1-2.5; Max: 3.7]]. miR-185-5p decreased following alcohol exposure [adjusted p-value <0.05, fold decrease 2 or more]. CONCLUSIONS: The microRNA composition of human serum is dynamic and environmental factors may have a significant impact. Within its context of use the fold change 'signal' of a microRNA must be large enough to negate the risk of false results due to background 'noise'.

Genetic architecture for hole-board behaviors across substantial time intervals in young, middle-aged and old mice.

A quantitative trait locus (QTL) analysis of behaviors across the life span was conducted in F(2) mice from a C57BL/6J x DBA/2J cross and 22 BXD recombinant inbred (RI) strains. Mice of three age groups were tested in a hole-board apparatus for 3 min on three occasions approximately 1 month apart (average age at test 150, 450 and 750 days, approximately 400 mice per group, divided equally by sex). Quantitative trait loci with small effect size were found on 11 chromosomes for hole-board activity (Hbact) and hole-board rearing (Hbrear). Analysis of 22 RI strains tested at 150 and 450 days of age found only suggestive linkage, with four QTL for Hbact overlapping with those from the F(2) analysis. There was a significant phenotypic correlation between Hbact and Hbrear (approximately 0.55-0.69) and substantial commonality among QTL for the two behaviors. QTL analyses of head-pokes (HP) and fecal boli (FB) only identified QTL at the suggestive level of significance. Age accounted for approximately 15% of the phenotypic variance (sex approximately 3%), and there were genotype by age interactions at approximately 25% of the Hbact and Hbrear QTL. Quantitative trait loci for Hbrear were relatively stable across the three measurement occasions (those for Hbact somewhat less so), although mean levels of each index declined markedly comparing the first to subsequent trials. Considered as a whole, the polygenic system influencing exploratory behaviors accounts for approximately the same amount of phenotypic variance as age (within the range studied), is stable across substantial periods of time, and acts, for the most part, independently of age and sex.

Evidence of isometric function of the flexor hallucis longus muscle in normal gait.

Studying mechanics of the muscles spanning multiple joints provides insights into intersegmental dynamics and movement coordination. Multiarticular muscles are thought to function at "near-isometric" lengths to transfer mechanical energy between the adjacent body segments. Flexor hallucis longus (FHL) is a multiarticular flexor of the great toe; however, its potential isometric function has received little attention. We used a robotic loading apparatus to investigate FHL mechanics during simulated walking in cadaver feet, and hypothesized that physiological force transmission across the foot can occur with isometric FHL function. The extrinsic foot tendons, stripped of the muscle fibers, were connected to computer-controlled linear actuators. The FHL activity was controlled using force-feedback (FC) based upon electromyographic data from healthy subjects, and subsequently, isometric positional feedback (PC), maintaining the FHL myotendinous junction stationary during simulated walking. Tendon forces and excursions were recorded, as were the strains within the first metatarsal. Forces in the metatarsal and metatarsophalangeal joint were derived from these strains. The FHL tendon excursion under FC was 6.57+/-3.13mm. The forces generated in the FHL tendon, metatarsal and metatarsophalangeal joint with the FHL under isometric PC were not significantly different in pattern from FC. These observations provide evidence that physiological forces could be generated along the great toe with isometric FHL function. A length servo mechanism such as the stretch reflex could likely control the isometric FHL function during in vivo locomotion; this could have interesting implications regarding the conditions of impaired stretch reflex such as spastic paresis and peripheral neuropathies.

Strontium administration in young chickens improves bone volume and architecture but does not enhance bone structural and material strength.

Genetic selection for rapid body growth in broiler chickens has resulted in adverse effects on the skeletal system exemplified by a higher rate of cortical fractures in leg bones. Strontium (Sr) has been reported to have beneficial effects on bone formation and strength. We supplemented the diet of 300-day-old chicks with increasing dosages of Sr (0%, 0.12%, or 0.24%) to study the capacity of the element to improve bone quality and mechanical integrity. Treatment with Sr increased cortical bone volume and reduced bone porosity as measured by micro-computed tomography. The higher level of Sr significantly reduced bone Ca content (34.7%) relative to controls (37.2%), suggesting that Sr replaced some of the Ca in bone. Material properties determined by the three-point bending test showed that bone in the Sr-treated groups withstood greater deformation prior to fracture. Load to failure and ultimate stress were similar across groups. Our results indicate that Sr treatment in rapidly growing chickens induced positive effects on bone volume but did not improve the breaking strength of long bones.

Acute effects of moderate intensity resistance exercise on bone cell activity.

Resistance exercise has positive effects on bone mass, but little is known about the mechanisms by which this occurs. The purpose of this study was to determine if a single bout of moderate intensity resistance exercise alters biochemical markers of bone cell activity. Indices of bone turnover were measured in nine healthy, untrained men (21.9 +/- 1.2 yrs old), before and following a single 45 minute session of resistance exercise, and during a control trial. A cross-over design was used so that all participants performed both trials in random order. Blood samples were collected immediately before, immediately after, and at 1, 8, 24, and 48 hours post exercise and analyzed for bone-specific alkaline phosphatase (BAP), type I collagen propeptide (PICP), and type I collagen N-telopeptide (sNTX). Urine from the second morning void was collected over four days (day before, day of, and two days following exercise) and analyzed for type I collagen N-telopeptide (uNTX). Exercise resulted in a significant increase (p < 0.05) in the ratio of biochemical markers of bone formation to bone resorption eight hours post exercise, largely due to a decrease in sNTX. Markers return to baseline within 24 hrs. These data suggest that moderate intensity resistance training acutely reduces bone resorption, leading to a favorable change in overall bone turnover, for at least 8 hours post exercise in untrained young men. Further work is needed to determine if long-term benefits to bone strength follow with persistent training.

A comparison of bone strain measurements at anatomically relevant sites using surface gauges versus strain gauged bone staples.

Instrumented bone staples were first introduced as an alternative to surface-mounted strain gauges for use in human in vivo bone strain measurements because their fixation to bone is secure and requires not only minimally invasive surgery. Bench-top bone bending models have shown that the output from strain gauged bone staples compares favorably to that of traditional mounted gauges. However their within- and across-subject performance at sites typically instrumented in vivo has never been examined. This study used seven human cadaver lower extremities with an age range of 23-81 years old and a dynamic gait simulator to examine and compare axial strains in the mid tibial diaphysis and on the dorsal surface of the second metatarsal as measured simultaneously with strain gauged bone staples and with traditional surface-mounted gauges. Rosette configurations were used at the tibial site for deriving principal compression and tension, and shear strains. Axial outputs from the two gauge types demonstrated strong linear relationships for the tibia (r(2)=0.78-0.94) and the second metatarsal (r(2)=0.96-0.99), but coefficients (slopes) for the relationship were variable (range 7-20), across subjects and across sites. The apparent low reliability of strain gauged staples may be explained by the fact that both strain gauged staples and surface strain gauges are inexact to some degree, do not measure strains from exactly the same areas and strain gauged staples reflect surface strains as well as deformations within the cortex. There were no relationships for the principal tibia compression, tension or shear strain measurements derived from the two rosette gauge types, reflecting the very different anatomical areas measured by each of the constructs in this study. Strain gauged bone staples may be most useful in comparing relative axial intra-subject differences between activities, but inter-subject variability may require larger sample sizes to detect differences between populations.

Metatarsal strains are sufficient to cause fatigue fracture during cyclic overloading.

Human in vivo tibial strains during vigorous walking have not been found to exceed 1200 microstrains. These values are below those found in ex vivo studies (>3000 microstrains) to cause cortical bone fatigue failure, suggesting that an intermediate bone remodeling response may be associated with tibial stress fractures. Metatarsal stress fractures, however, often develop before there is time for such a response to occur. Simultaneous in vivo axial strains were measured at the mid diaphysis of the second metatarsal and the tibia in two subjects. Peak axial metatarsal compression strains and strain rates were significantly higher than those of the tibia during treadmill walking and jogging both barefoot and with running shoes and during simple calisthenics. During barefoot treadmill walking metatarsal compression strains were greater than 2500 microstrains. During one- and two-leg vertical jumps and broad jumping, both metatarsal compression and tension strains were >3000 microstrains. Compression and tension strains in the metatarsus unlike those of the tibia may be sufficiently high even during moderate exertional activities to cause fatigue failure of bone secondary to the number of loading cycles without an intermediate bone remodeling response.

Changes in muscle moment arms following split tendon transfer of tibialis anterior and tibialis posterior.

Moment arms of tibialis anterior (TA) and tibialis posterior (TP) about the subtalar and talocrural joint axes were measured in anatomic specimens both before and after split tendon transfers. These procedures are commonly performed to correct hindfoot varus, a gait deformity that is often seen in patients with cerebral palsy, stroke, and brain injury. Split tendon transfer significantly reduced the inversion moment arms of tibialis anterior and tibialis posterior at all subtalar joint angles except for the most everted position in the case of TA. Changes in subtalar joint moment arms produced by split tendon transfer, especially those seen in TA, were variable, suggesting that the procedure may be susceptible to technical errors, especially related to balancing tensions in the medial and lateral tendon halves. Talocrural joint moment arms of both muscles were preserved following split tendon transfer. This study presents the first measurements of the moment arms of split transferred muscles. These characterizations of the mechanics of split tendon transfer will aid in the planning and assessment of these procedures.

Effect of rearfoot orthotics on postural sway after lateral ankle sprain.

OBJECTIVE: To investigate the effects of different rearfoot orthotics on postural sway during unilateral stance after lateral ankle sprain. DESIGN: Repeated-measures 3-factor analysis of variance on postural sway length and velocity in the frontal and sagittal planes with factors being stance leg (injured, uninjured), session (within 3 d, 2 wk, 4 wk postinjury), and condition (6 orthotic conditions). SETTING: University biomechanics laboratory. PATIENTS: Fifteen collegiate athletes with acute, unilateral first- or second-degree lateral ankle sprain. INTERVENTIONS: Balance testing was performed under 6 conditions: (1) shoe only, (2) molded Aquaplast orthotic, (3) lateral heel wedge, (4) 7 degrees medially posted orthotic, (5) 4 degrees laterally posted orthotic, and (6) neutral orthotic. MAIN OUTCOME MEASURES: Postural sway length and postural sway velocity in the frontal and sagittal planes. RESULTS: Significant main effects were found for side and session, but not orthotic condition, for all 4 dependent variables. Postural sway length and velocity were greater on the injured limbs as compared with the uninjured limbs during the first 2 sessions but not during the third session. None of the orthotics significantly reduced postural sway compared with the shoe-only condition after lateral ankle sprain. CONCLUSIONS: Rearfoot orthotics, irrespective of design or posting, were ineffective at improving postural sway after lateral ankle sprain.

In vitro modeling of human tibial strains during exercise in micro-gravity.

Prolonged exposure to micro-gravity causes substantial bone loss (Leblanc et al., Journal of Bone Mineral Research 11 (1996) S323) and treadmill exercise under gravity replacement loads (GRLs) has been advocated as a countermeasure. To date, the magnitudes of GRLs employed for locomotion in space have been substantially less than the loads imposed in the earthbound 1G environment, which may account for the poor performance of locomotion as an intervention. The success of future treadmill interventions will likely require GRLs of greater magnitude. It is widely held that mechanical tissue strain is an important intermediary signal in the transduction pathway linking the external loading environment to bone maintenance and functional adaptation; yet, to our knowledge, no data exist linking alterations in external skeletal loading to alterations in bone strain. In this preliminary study, we used unique cadaver simulations of micro-gravity locomotion to determine relationships between localized tibial bone strains and external loading as a means to better predict the efficacy of future exercise interventions proposed for bone maintenance on orbit. Bone strain magnitudes in the distal tibia were found to be linearly related to ground reaction force magnitude (R(2)>0.7). Strain distributions indicated that the primary mode of tibial loading was in bending, with little variation in the neutral axis over the stance phase of gait. The greatest strains, as well as the greatest strain sensitivity to altered external loading, occurred within the anterior crest and posterior aspect of the tibia, the sites furthest removed from the neutral axis of bending. We established a technique for estimating local strain magnitudes from external loads, and equations for predicting strain during simulated micro-gravity walking are presented.

Contributions of active and passive toe flexion to forefoot loading.

Toe flexion during terminal stance has an active component contributed by the muscles that flex the toes and a passive component contributed by the plantar fascia. This study examined the relative importance of these two mechanisms in maintaining proper force sharing between the toes and forefoot. Thirteen nonpaired cadaver feet were tested in a dynamic gait stimulator, which reproduces the kinematics and kinetics of the foot, ankle, and tibia by applying physiologic muscle forces and proximal tibial kinematics. The distribution of plantar pressure beneath the foot was measured at the terminal stance phase of gait under normal extrinsic muscle activity with an intact plantar fascia, in the absence of extrinsic toe flexor activity (no flexor hallucis longus or flexor digitorum longus) with an intact plantar fascia, and after complete fasciotomy with normal extrinsic toe flexor activity. In the absence of the toe flexor muscles or after plantar fasciotomy the contact area decreased beneath the toes and contact force shifted from the toes to the metatarsal heads. In addition, pressure distribution beneath the metatarsal heads after fasciotomy shifted laterally and posteriorly, indicating that the plantar fascia enables more efficient force transmission through the high gear axis during locomotion. The plantar fascia enables the toes to provide plantar-directed force and bear high loads during push-off.

Bone strain and microcracks at stress fracture sites in human metatarsals.

Microcracks in bone have been implicated in the development of stress fractures. The goal of this study was to evaluate bone strain and microcracks at locations where stress fractures are common (second metatarsal diaphysis) and rare (fifth metatarsal diaphysis) in an attempt to increase our understanding of the pathogenesis of stress fractures. A dynamic gait simulator was used to simulate normal walking with cadaver feet. The feet were loaded over the entire stance phase of gait and diaphyseal strains were recorded in second and fifth metatarsals. Microcrack density (Cr.Dn) and surface density (Cr.S.Dn) were determined in metatarsal cross sections from the contralateral feet. Bone strain was significantly higher in second metatarsals (-1897 +/- 613 microstrain) than in fifth metatarsals (-908 +/- 503 microstrain). However, second metatarsal Cr.Dn (0.23 +/- 0.15 #/mm(2)) was not significantly different from fifth metatarsal Cr.Dn (0.35 +/- 0.19 #/mm(2)). There was also no significant difference between Cr.S.Dn in second (17.64 +/- 10.99 microm/mm(2)) and fifth (26.70 +/- 15.53 microm/mm(2)) metatarsals. There were no significant relationships between the microcrack parameters and peak strain in either metatarsal. Cracks that occurred in trabecular struts (92 +/- 33 microm) were significantly longer than those found ending at cement lines (71 +/- 15 microm) and within osteons (57 +/- 16 microm). There were no significant relationships between the microcrack parameters and age in either metatarsal. Peak strain was more than twofold greater in second metatarsals than in fifth metatarsals for simulations of normal walking; however, microcrack parameters were unable to explain the greater incidence of second metatarsal stress fractures.

The role of exercise in the prevention and treatment of osteoporosis and osteoarthritis.

Osteoporosis and osteoarthritis are two distinctly different rheumatic conditions that target elderly, primarily female, populations. This article examines the scientific evidence supporting the use of exercise as a specific therapeutic modality, the general physiologic and psychological benefits of exercise, and the exercise programs currently recommended to combat these prevalent musculoskeletal disorders. Exercise is a valuable adjunct to treatment programs aimed at alleviating the risks and symptoms of osteoporosis and osteoarthritis. In addition to its potential impact on the disease processes themselves, exercise improves general health and well being, enhances quality of life, and preserves physical independence.

Strains in the metatarsals during the stance phase of gait: implications for stress fractures.

BACKGROUND: Stress fractures of the metatarsals are common overuse injuries in athletes and military cadets, yet their etiology remains unclear. In vitro, high bone strains have been associated with the accumulation of microdamage and shortened fatigue life. It is therefore postulated that stress fractures in vivo are caused by elevated strains, which lead to the accumulation of excessive damage. We used a cadaver model to test the hypothesis that strains in the metatarsals increase with simulated muscle fatigue and plantar fasciotomy. METHODS: A dynamic gait simulator was used to load fifteen cadaveric feet during the entire stance phase of gait under conditions simulating normal walking, walking with fatigue of the auxiliary plantar flexors, and walking after a plantar fasciotomy. Strains were measured, with use of axial strain-gauges, in the dorsal, medial, and lateral aspects of the diaphysis of the second and fifth metatarsals as well as in the proximal metaphysis of the fifth metatarsal. RESULTS: When the feet were loaded under normal walking conditions, the mean peak strain in the dorsal aspect of the second metatarsal (-1897 microstrain) was more than twice that in the medial aspect of the fifth metatarsal (-908 microstrain). Simulated muscle fatigue significantly increased peak strain in the second metatarsal and decreased peak strain in the fifth metatarsal. Release of the plantar fascia caused significant alterations in strain in both metatarsal bones; these alterations were greater than those caused by muscle fatigue. After the plantar fasciotomy, the mean peak strain in the dorsal aspect of the second metatarsal (-3797 microstrain) was twice that under normal walking conditions. CONCLUSIONS: The peak axial strain in the diaphysis of the second metatarsal is significantly (p < 0.0001) higher than that in the diaphysis of the fifth metatarsal during normal gait. The plantar fascia and the auxiliary plantar flexors are important for maintaining normal strains in the metatarsals during gait.

Unilateral elbow arthrodesis: the preferred position.

Twenty-five volunteers had unilateral elbow immobilization for 24 hours in each of two positions of flexion, 45 degrees and 90 degrees . Twenty-two of the 25 volunteers preferred a position of 90 degrees of flexion. Standard functional testing revealed significant limitations in each position of immobilization, confirming that there is no single optimal position of elbow arthrodesis. This study suggests that, for most individuals, 90 degrees is the preferred position of elbow arthrodesis for activities of daily living. However, factors such as age, sex, occupation, and dominance of the extremity should be considered when choosing a position of arthrodesis.

Biomechanical evaluation of impaction fractures of the femoral head.

OBJECTIVES: To measure the effect of an impaction fracture of the femoral head on load transmission in the hip joint. DESIGN: We measured the contact areas and pressure between the acetabulum and femoral head of cadaveric pelves in four different conditions: intact, with an operatively created one-square-centimeter defect in the superior femoral head, with a two-square-centimeter defect, and with a four-square-centimeter defect. All defects were uniformly three millimeters deep. SETTING: Hips were loaded in a simulated single-limb stance. Pressure and area measurements were made with Fuji pressure-sensitive film. SPECIMENS: Seven hip joints in seven whole pelves were tested. MAIN OUTCOME MEASUREMENTS: Contact area, load, and mean and maximum pressures were measured. RESULTS: Peripheral loading was seen in the intact acetabulum. This was not disrupted after impaction fractures of any size. A significant increase in mean maximum pressures in the superior acetabulum was seen with two-square-centimeter and four-square-centimeter defects. CONCLUSIONS: In contrast to prior biomechanical studies of acetabular fractures, our investigation revealed that disruption of the peripheral distribution of load does not occur with impaction fractures of the femoral head. Clinical series indicate that impaction injuries to the femoral head are associated with a poor prognosis. Previous biomechanical data on acetabular fracture patterns associated with a poor prognosis have shown increases in mean and peak pressures in the superior acetabulum. This was seen with two-square-centimeter and four-square-centimeter impaction injuries. Other factors, such as wear of the articular cartilage during joint motion or associated microscopic damage to the remainder of the joint surface at the time of injury, may also contribute to the rapid joint deterioration seen in these injuries. Further study is indicated.

Forearm interosseous ligament isometry.

Biomechanical testing was performed to determine isometric interosseous ligament graft placement as a preliminary step for reconstruction after an axial forearm disruption. Twenty-five combinations of potential ligament graft placement were studied on 7 fresh-frozen cadavers. Suture was used to simulate these potential ligament reconstructions, and suture excursion was used as an index of isometry. Ligament orientation was defined by the angle formed between the ulna and the suture (surrogate graft). Ligament position was defined by its insertion on the ulna as a percentage of ulna length. Suture-ulna angles from 9 degrees to 38 degrees produced significantly less suture excursion than angles of > or = 39 degrees. Minimal suture excursion was noted at angles of < or = 20 degrees, which we feel represents the optimal range for reconstruction. The optimal location on the ulna for isometric interosseous ligament reconstruction was at 25% to 30% of total ulna length, as measured proximally from the distal ulna articular surface. The radius isometric location is optimally located by a vector starting from the ulna isometric point and directed toward the proximal radius at an angle of < or = 20 degrees relative to the long axis of the ulna. Interosseous ligament reconstruction may prove beneficial in the long-term outcome of reconstruction after axial forearm disruption.

Biomechanical consequences of plantar fascial release or rupture during gait. Part II: alterations in forefoot loading.

With a model using feet from cadavers, we tested the hypothesis that plantar fascial release or rupture alters the loading environment of the forefoot during the latter half of the stance phase of gait. The model simulated the position and loading environment of the foot at two instants: early in terminal stance immediately after heel-off and late in terminal stance just preceding contralateral heel strike. Eight feet were loaded at both positions by simulated plantar flexor contraction, and the distribution of plantar pressure was measured before and after progressive release of the plantar fascia. Strain in the diaphysis of the second metatarsal was also measured, from which the bending moments and axial force imposed on the metatarsal were calculated. Cutting the medial half of the central plantar fascial band significantly increased peak pressure under the metatarsal heads but had little effect on pressures in other regions of the forefoot or on second metatarsal strain and loading. Dividing the entire central band or completely releasing the plantar fascia from the calcaneus had a much greater effect and caused significant shifts in plantar pressure and force from the toes to beneath the metatarsal heads. These shifts were accompanied by significantly increased strain and bending in the second metatarsal. Complete fasciotomy increased the magnitude of strain in the dorsal aspect of the second metatarsal by more than 80%, suggesting that plantar fascial release or rupture accelerates the accumulation of fatigue damage in these bones. Altered forefoot loading may be a potential complication of plantar fasciotomy.