Differences by Sex in Association of Mental Health With Video Gaming or Other Nonacademic Computer Use Among US Adolescents.

INTRODUCTION: Although numerous studies have examined the association between playing video games and cognitive skills, aggression, and depression, few studies have examined how these associations differ by sex. The objective of our study was to determine differences by sex in association between video gaming or other nonacademic computer use and depressive symptoms, suicidal behavior, and being bullied among adolescents in the United States. METHODS: We used data from the 2015 Youth Risk Behavior Survey on 15,624 US high school students. Rao-Scott χ2 tests, which were adjusted for the complex sampling design, were conducted to assess differences by sex in the association of mental health with video gaming or other nonacademic computer use. RESULTS: Approximately one-fifth (19.4%) of adolescents spent 5 or more hours daily on video gaming or other nonacademic computer use, and 17.9% did not spend any time in those activities. A greater percentage of female adolescents than male adolescents reported spending no time (22.1% and 14.0%, respectively) or 5 hours or more (21.3% and 17.5%, respectively) in gaming and other nonacademic computer use (P < .001). The association between mental problems and video gaming or other nonacademic computer use differed by sex. Among female adolescents, prevalence of mental problems increased steadily in association with increased time spent, whereas the pattern for male adolescents followed a J-shaped curve, decreasing initially, increasing slowly, and then increasing rapidly beginning at 4 hours or more. CONCLUSION: Female adolescents were more likely to have all 3 mental health problems than male adolescents were. Spending no time or 5 hours or more daily on video gaming or other nonacademic computer use was associated with increased mental problems among both sexes. As suggested by the J-shaped relationship, 1 hour or less spent on video gaming or other nonacademic computer use may reduce depressive symptoms, suicidal behavior, and being bullied compared with no use or excessive use.

Simulating the Lunar Environment: Partial Weightbearing and High-LET Radiation-Induce Bone Loss and Increase Sclerostin-Positive Osteocytes.

Exploration missions to the Moon or Mars will expose astronauts to galactic cosmic radiation and low gravitational fields. Exposure to reduced weightbearing and radiation independently result in bone loss. However, no data exist regarding the skeletal consequences of combining low-dose, high-linear energy transfer (LET) radiation and partial weightbearing. We hypothesized that simulated galactic cosmic radiation would exacerbate bone loss in animals held at one-sixth body weight (G/6) without radiation exposure. Female BALB/cByJ four-month-old mice were randomly assigned to one of the following treatment groups: 1 gravity (1G) control; 1G with radiation; G/6 control; and G/6 with radiation. Mice were exposed to either silicon-28 or X-ray radiation. (28)Si radiation (300 MeV/nucleon) was administered at acute doses of 0 (sham), 0.17 and 0.5 Gy, or in three fractionated doses of 0.17 Gy each over seven days. X radiation (250 kV) was administered at acute doses of 0 (sham), 0.17, 0.5 and 1 Gy, or in three fractionated doses of 0.33 Gy each over 14 days. Bones were harvested 21 days after the first exposure. Acute 1 Gy X-ray irradiation during G/6, and acute or fractionated 0.5 Gy (28)Si irradiation during 1G resulted in significantly lower cancellous mass [percentage bone volume/total volume (%BV/TV), by microcomputed tomography]. In addition, G/6 significantly reduced %BV/TV compared to 1G controls. When acute X-ray irradiation was combined with G/6, distal femur %BV/TV was significantly lower compared to G/6 control. Fractionated X-ray irradiation during G/6 protected against radiation-induced losses in %BV/TV and trabecular number, while fractionated (28)Si irradiation during 1G exacerbated the effects compared to single-dose exposure. Impaired bone formation capacity, measured by percentage mineralizing surface, can partially explain the lower cortical bone thickness. Moreover, both partial weightbearing and (28)Si-ion exposure contribute to a higher proportion of sclerostin-positive osteocytes in cortical bone. Taken together, these data suggest that partial weightbearing and low-dose, high-LET radiation negatively impact maintenance of bone mass by lowering bone formation and increasing bone resorption. The impaired bone formation response is associated with sclerostin-induced suppression of Wnt signaling. Therefore, exposure to low-dose, high-LET radiation during long-duration spaceflight missions may reduce bone formation capacity, decrease cancellous bone mass and increase bone resorption. Future countermeasure strategies should aim to restore mechanical loads on bone to those experienced in one gravity. Moreover, low-doses of high-LET radiation during long-duration spaceflight should be limited or countermeasure strategies employed to mitigate bone loss.

Simulated resistance training, but not alendronate, increases cortical bone formation and suppresses sclerostin during disuse.

Mechanical loading modulates the osteocyte-derived protein sclerostin, a potent inhibitor of bone formation. We hypothesized that simulated resistance training (SRT), combined with alendronate (ALEN) treatment, during hindlimb unloading (HU) would most effectively mitigate disuse-induced decrements in cortical bone geometry and formation rate (BFR). Sixty male, Sprague-Dawley rats (6-mo-old) were randomly assigned to either cage control (CC), HU, HU plus either ALEN (HU+ALEN), or SRT (HU+SRT), or combined ALEN and SRT (HU+SRT/ALEN) for 28 days. Computed tomography scans on days -1 and 28 were taken at the middiaphyseal tibia. HU+SRT and HU+SRT/ALEN rats were subjected to muscle contractions once every 3 days during HU (4 sets of 5 repetitions; 1,000 ms isometric + 1,000 ms eccentric). The HU+ALEN and HU+SRT/ALEN rats received 10 µg/kg ALEN 3 times/wk. Compared with the CC animals, HU suppressed the normal slow growth-induced increases of cortical bone mineral content, cortical bone area, and polar cross-sectional moment of inertia; however, SRT during HU restored cortical bone growth. HU suppressed middiaphyseal tibia periosteal BFR by 56% vs. CC (P < 0.05). However, SRT during HU restored BFR at both periosteal (to 2.6-fold higher than CC) and endocortical (14-fold higher than CC) surfaces (P < 0.01). ALEN attenuated the SRT-induced BFR gains during HU. The proportion of sclerostin-positive osteocytes in cortical bone was significantly higher (+121% vs. CC) in the HU group; SRT during HU effectively suppressed the higher proportion of sclerostin-positive osteocytes. In conclusion, a minimum number of high-intensity muscle contractions, performed during disuse, restores cortical BFR and suppress unloading-induced increases in sclerostin-positive osteocytes.

Increased training loads do not magnify cancellous bone gains with rodent jump resistance exercise.

This study sought to elucidate the effects of a low- and high-load jump resistance exercise (RE) training protocol on cancellous bone of the proximal tibia metaphysis (PTM) and femoral neck (FN). Sprague-Dawley rats (male, 6 mo old) were randomly assigned to high-load RE (HRE; n = 16), low-load RE (LRE; n = 15), or sedentary cage control (CC; n = 11) groups. Animals in the HRE and LRE groups performed 15 sessions of jump RE during 5 wk of training. PTM cancellous volumetric bone mineral density (vBMD), assessed by in vivo peripheral quantitative computed tomography scans, significantly increased in both exercise groups (+9%; P < 0.001), resulting in part from 130% (HRE; P = 0.003) and 213% (LRE; P < 0.0001) greater bone formation (measured by standard histomorphometry) vs. CC. Additionally, mineralizing surface (%MS/BS) and mineral apposition rate were higher (50-90%) in HRE and LRE animals compared with controls. PTM bone microarchitecture was enhanced with LRE, resulting in greater trabecular thickness (P = 0.03) and bone volume fraction (BV/TV; P = 0.04) vs. CC. Resorption surface was reduced by nearly 50% in both exercise paradigms. Increased PTM bone mass in the LRE group translated into a 161% greater elastic modulus (P = 0.04) vs. CC. LRE and HRE increased FN vBMD (10%; P < 0.0001) and bone mineral content (∼ 20%; P < 0.0001) and resulted in significantly greater FN strength vs. CC. For the vast majority of variables, there was no difference in the cancellous bone response between the two exercise groups, although LRE resulted in significantly greater body mass accrual and bone formation response. These results suggest that jumping at minimal resistance provides a similar anabolic stimulus to cancellous bone as jumping at loads exceeding body mass.

What can we learn about patient safety from information sources within an acute hospital: a step on the ladder of integrated risk management?

OBJECTIVE: To assess the utility of data already existing within hospitals for monitoring patient safety. SETTING: An acute hospital in southern England. DESIGN: Mapping of data sources proposed by staff as potentially able to identify patient safety issues followed by an in-depth analysis of the content of seven key sources. Data source analysis: For each data source: scope and depth of content in relation to patient safety, number and type of patient safety incidents identified, degree of overlap with incidents identified by different sources, levels of patient harm associated with incidents. RESULTS: A wide range of data sources existing within the hospital setting have the potential to provide information about patient safety incidents. Poor quality of coding, delays in reports reaching databases, the narrow focus of some data sources, limited data-collection periods and lack of central collation of findings were some of the barriers to making the best use of routine data sources for monitoring patient safety. An in-depth analysis of seven key data sources (Clinical Incident database, Health and Safety Incident database, Complaints database, Claims database and Inquest database, the Patient Administration System and case notes) indicated that case notes have the potential to identify the largest number of incidents and provide the richest source of information on such incidents. The seven data sources identified different types of incidents with differing levels of patient harm. There was little overlap between the incidents identified by different sources. CONCLUSION: Despite issues related to the quality of coding, depth of information available and accessibility, triangulating information from more than one source can identify a broader range of incidents and provide additional information related to professional groups involved, types of patients affected and important contributory factors. Such an approach can provide a focus for further work and ultimately contributes to the identification of appropriate interventions that improve patient safety.

Molt performance and bone density of cortical, medullary, and cancellous bone in laying hens during feed restriction or alfalfa-based feed molt.

A study was conducted to evaluate the effects of alfalfa-based molt diets on molting performance and bone qualities. A total of 36 Single Comb White Leghorn hens were used for the study. There were 6 treatments: pretrial control (PC), fully fed (FF), feed withdrawal (FW), 90% alfalfa:10% layer ration (A90), 80% alfalfa:20% layer ration (A80), and 70% alfalfa:30% layer ration (A70). For the PC treatment, hens were euthanized by CO(2) gas, and bones were collected before molt was initiated. At the end of the 9-d molt period, hens were euthanized, and femurs and tibias were collected to evaluate bone qualities by peripheral quantitative computed tomography, mechanical testing, and conventional ash weights. The hens fed alfalfa-based molt diets and FW stopped laying eggs within 5 d after molt started, and all hens in these groups had reduced ovary weights compared with those of the FF hens. In the FW and A90 groups, total femur volumetric bone mineral densities (vBMD) at the midshaft were significantly lower, but those of the A80 and A70 groups were not significantly different from the values for the PC and FF hens. In cortical bone density, the midshaft tibial vBMD were significantly higher for FF and A70 hens than for PC hens. The medullary bone densities at the midshaft femur or tibia of the FW, A90, A80, and A70 hens were reduced compared with those of the PC hens. Femur cancellous densities at the distal femur for the FW and A90 hens were significantly reduced compared with those of the PC and FF hens. The FW, A80, and A70 hens yielded significantly higher elastic moduli, and the A80 hens had higher ultimate stress compared with the PC hens, suggesting that the mechanical integrity of the midshaft bone was maintained even though the medullary vBMD was reduced. These results suggest that alfalfa-based molt diets exhibit molt performance similar to FW, that medullary and cancellous bones are labile bone compartments during molting, and that alfalfa-based molt diets may be beneficial to maintain the mechanical properties of bones during molt.

Consultants' attitudes to clinical governance: barriers and incentives to engagement.

OBJECTIVE: To explore medical specialists' attitudes to clinical governance in acute hospitals and factors influencing these attitudes. METHODS: A semi-structured interview study with a purposeful sample of 24 medical specialists from two contrasting hospitals. Hospital A had a low level of consultant involvement in quality improvement initiatives and Hospital B had higher levels of engagement. RESULTS: Specialists from both hospitals acknowledged that quality improvement was a major part of their role. Among specialists from Hospital A, the lack of a commonly held focus on quality-improvement, poor inter-professional relationships and little clinical engagement in management were the main factors generating negative attitudes towards clinical governance. Effective communication of the hospital's goal of continuous quality improvement to all staff groups, a sense of being able to get issues affecting the quality of care heard by senior management, and a perception that there were clear structures and processes to support clinical governance, were factors that resulted in a more positive attitude to clinical governance among specialists in Hospital B. Specialists from both hospitals identified lack of time across all professional groups and availability of accurate data as barriers to involvement in clinical governance activities. CONCLUSION: The cultural context, level of technical support available, ability to communicate clear goals and strategies and the presence of structures to support delivery, all contribute to shaping specialists' attitudes to clinical governance and in turn influence levels of engagement and ultimately the success of quality improvement initiatives.

Differential bone and muscle recovery following hindlimb unloading in skeletally mature male rats.

This study was designed to track the recovery of bone and muscle properties after 28 days of hindlimb unloading (HU) in skeletally mature male rats in order to quantify the degree and timing of the expected mismatch between bone and muscle properties. Outcome variables were in vivo plantarflexor peak isometric torque and proximal tibial volumetric bone mineral density (vBMD). Proximal tibia vBMD was significantly lower than age-matched controls (-7.8%) after 28 days of HU, continued to decrease through day 28 of recovery (-10%) and did not recover until day 84 of recovery. Plantarflexor peak isometric torque was significantly reduced after 28 days of HU (-13.9%). Further reductions of isometric torque occurred after 7 days of recovery (-15%), but returned to age-matched control levels by day 14. The functional relationship between bone and muscle (vBMD/isometric torque) tended to increase after 28 days of HU (+7.8%), remained elevated after 7 days of reloading (+9.1%) and was significantly lower than age-matched controls on day 28 (-13.6%). This relatively rapid return of muscle strength, coupled with continued depression of bone density at the proximal tibia metaphysis, may increase the risk for skeletal injury during recovery from prolonged periods of reduced mechanical loading.

Effects of eccentric exercise training on cortical bone and muscle strength in the estrogen-deficient mouse.

The purpose of this study was to determine whether eccentrically biased exercise training could attenuate changes in muscle and bone function associated with estrogen deficiency in the mouse model. Four groups of ICR mice were used: control (Con), sham ovariectomized (Sham), ovariectomized (OVX), and ovariectomized + high-force resistance training (OVX+Train). All groups except Con were implanted with a nerve cuff surrounding the peroneal nerve to stimulate the left ankle dorsiflexors. Training consisted of 30 stimulated eccentric contractions of the left ankle dorsiflexors at approximately 150% of peak isometric torque every third day for 8 wk. After the training period, groups were not significantly different with regard to peak torque or muscle size. However, the tibial midshaft of the trained leg in the OVX+Train mice exhibited greater stiffness (+15%) than that in the untrained OVX mice, which could not be explained by changes in cross-sectional geometry of the tibia. Scaling of bone mechanical properties to muscle strength were not altered by ovariectomy or training. These data indicate that eccentric exercise training in adult mice can significantly increase bone stiffness, despite the absence of ovarian hormones.

Specialist vaccination advice and pockets of resistance to MMR vaccination: lessons from an outbreak of measles.

An outbreak of measles was associated with a private nursery school in north west London. Sixteen cases were identified of whom 13 were laboratory confirmed. The majority of cases were aged three years or younger. Older cases were siblings of younger cases. None of the cases had been vaccinated against measles. In the nursery school 33% of the children had not received MMR vaccination. Based on specialist advice from the Health Protection Agency the outbreak control team recommended that children with no history of MMR vaccination should have a first MMR dose as soon as possible and that children with one MMR dose should receive the second dose as soon as possible (minimum of one month between doses). Some parents had strong negative views about MMR and represented 'pockets of resistance' to vaccination advice. The specialist vaccination advice, which was different to national immunisation guidelines, also caused some confusion amongst other health professionals. With a decrease in MMR vaccination uptake and resulting increased potential for future measles outbreaks, clinicians should be aware of and understand specialist vaccination advice intended to deal with outbreaks.

Site- and compartment-specific changes in bone with hindlimb unloading in mature adult rats.

The purpose of this study was to examine site- and compartment-specific changes in bone induced by hindlimb unloading (HU) in the mature adult male rat (6 months old). Tibiae, femora, and humeri were removed after 14, 21, and 28 days of HU for determination of bone mineral density (BMD) and geometry by peripheral quantitative computed tomography (pQCT), mechanical properties, and bone formation rate (BFR), and compared with baseline (0 day) and aging (28 day) controls. HU resulted in 20%-21% declines in cancellous BMD at the proximal tibia and femoral neck after 28 day HU vs. 0 day controls (CON). Cortical shell BMD at these sites was greater (by 4%-6%) in both 28 day HU and 28 day CON vs. 0 day CON animals, and nearly identical to that gain seen in the weight-bearing humerus. Mechanical properties at the proximal tibia exhibited a nonsignificant decline after HU vs. those of 0 day CON rats. At the femoral neck, a 10% decrement was noted in ultimate load in 28 day HU rats vs. 28 day CON animals. Middiaphyseal tibial bone increased slightly in density and area during HU; no differences in structural and material properties between 28 day HU and 28 day CON rats were noted. BFR at the tibial midshaft was significantly lower (by 90%) after 21 day HU vs. 0 day CON; this decline was maintained throughout 28 day HU. These results suggest there are compartment-specific differences in the mature adult skeletal response to hindlimb unloading, and that the major impact over 28 days of unloading is on cancellous bone sites. Given the sharp decline in BFR for midshaft cortical bone, it appears likely that deficits in BMD, area, or mechanical properties would develop with longer duration unloading.

Material properties of Thera-Band Tubing.

BACKGROUND AND PURPOSE: Thera-Band Tubing has been used in rehabilitation to provide resistance for exercise and splinting. However, the forces required to stretch the tubing have not been thoroughly quantified. Therefore, the therapist cannot assess, with certainty, how much force is applied when using a given length and type of Thera-Band Tubing. The purpose of this study was to quantify the material properties of Thera-Band Tubing. METHODS: Force versus percentage of strain for all types of Thera-Band Tubing was measured during elongation in a mechanical testing machine. RESULTS: The material is very compliant and displays nonlinear behavior in the initial stretching phase and linear behavior after 50% elongation. DISCUSSION AND CONCLUSION: From the data obtained in this project, plots that can provide the therapist with information about the forces needed for exercises with Thera-Band Tubing were generated. These data should allow therapists to make better choices about which size of tubing to use for each patient.

Comparison of bending modulus and yield strength between outer stratum medium and stratum medium zona alba in equine hooves.

OBJECTIVE: To determine whether the bending modulus and yield strength of the outer stratum medium (SM) differed from those of the SM zona alba (SMZA) and to what degree they differed. In addition, a comparison was made among our values and values reported elsewhere. SAMPLE POPULATION: 10 normal equine feet. PROCEDURE: A 3-point bending technique was used to determine the bending modulus and yield strength of the outer SM and SMZA. Efforts were made to minimize biological and technical factors that could influence the bending modulus. RESULTS: Bending modulus of the outer SM was (mean +/- SD) 187.6 +/- 41.3 MPa, whereas mean value for the SMZA was 98.2 +/- 36.8 MPa. Mean yield strength was 19.4 +/- 2.6 MPa for the outer SM and 5.6 +/- 1.7 MPa for the SMZA. Values for bending modulus and yield strength differed significantly between the outer SM and SMZA. Significant differences were not detected when the outer SM was loaded in bending from the outer or inner surface. CONCLUSIONS AND CLINICAL RELEVANCE: Potentially, the SMZA could serve as a mechanical buffer zone between the rigid hoof wall and bone and laminar tissues. This buffer zone potentially assists the feet of horses in transmitting a load through the tissues and prevents the most susceptible tissues from becoming damaged. More consistency among tissue selection, preparation, and testing protocols must be attained before an accurate 3-dimensional finite-element model of an equine foot can be constructed.

Adult-onset alcohol consumption induces osteopenia in female rats.

BACKGROUND: Alcohol is a known risk factor for osteopenia and fracture in humans, and its effects on the skeleton have been studied extensively in animal models. Almost all studies of rats, however, have begun rats on alcohol diets while the animals were young and still growing. The purpose of the current study was to examine the effects of alcohol consumption on rats that began drinking alcohol as adults, so that the confounding effects of growth might be minimized. METHODS: Nine-month-old female Sprague-Dawley rats were studied for two durations (8 and 14 weeks). The following diet groups were used for both durations: alcohol (n = 7), in which rats were fed a liquid diet containing ethanol (8.1% v/v; Lieber-DeCarli method); pair-fed (n = 7), in which rats were fed a caloric-equivalent liquid diet matched to the alcohol-fed animals; and pellet (n = 6), in which rats consumed standard rat chow and water. A cessation protocol was also used in which alcohol- and pair-fed groups were fed liquid diets for 8 weeks and then given pellet chow and water for 6 weeks, with pair feeding maintained during the cessation period. RESULTS: Only minor effects developed in the rats in the 8-week group, but after 14 weeks, the cancellous bone of the proximal tibia was severely osteopenic in the alcohol-fed animals. The bone volume and trabecular number were both significantly lower in the alcohol-fed animals than in the pair-fed and pellet-fed control animals and also lower than in the alcohol-fed animals in the 8-week group. Mechanical properties of the cancellous bone in the distal femur also were significantly diminished in the 14-week alcohol-fed group. Composition and mechanical properties of the cortical bone in the femur diaphysis were largely unaffected, but the yield stress was significantly lower in the 14-week alcohol-fed group than in the 8-week alcohol-fed group. No significant effects were found in the cessation groups with regard to almost all parameters measured. CONCLUSIONS: Our study results demonstrate that chronic adult-onset alcohol consumption leads to significantly diminished cancellous bone properties and that these effects depend on the duration of alcohol use.

The mechanical properties of cancellous bone in the proximal tibia of ovariectomized rats.

The "mature rat model" is an effective and often-used surrogate for studying mechanisms and characteristics of estrogen-deficient osteopenia. The purpose of this study was to extend our understanding of this animal model to include the mechanical properties of cancellous bone in the proximal tibia. Female Sprague-Dawley rats were divided into two groups (n=13 each) at 14 weeks of age: an ovariectomized group (OVX) and a sham-operated control group (sham). The study terminated after a duration of 5 weeks. Specimens 2 mm long were cut from the proximal tibial metaphysis just below the growth plate and tested using two methods: (1) "whole-slice" compression, in which the entire specimen is loaded between two larger flat platens and (2) "reduced-platen" compression (RPC), which uses platens sized and aligned to load only the cancellous bone in the center of the sample. Three-point bending tests also were conducted on the femur. The short duration of estrogen deficiency yielded only minimal differences (< 10%) in femoral cortical bone but dramatic reductions (approximately 60%) in cancellous bone properties as determined by the RPC method. Ultimate stress was 7.23 MPa +/- 1.97 MPa for OVX versus 18.1 MPa +/- 5.21 MPa for sham; and elastic modulus was 252 MPa +/- 104 MPa for OVX versus 603 MPa +/- 180 MPa for sham. These changes in mechanical properties are similar in many respects to the dramatic effects reported in histomorphometric studies. For the whole-slice method, differences in mechanical properties between the two groups were not as large because the test directly loads both cancellous and cortical bone, and the latter is not affected as severely by estrogen deficiency. In this case, ultimate stress and elastic modulus were only 30% (or less) lower for the OVX group.

Disuse bone loss in hindquarter suspended rats: partial weightbearing, exercise and ibandronate treatment as countermeasures.

The purpose of this study was to evaluate potential countermeasures for bone loss during long-term space missions in the hindquarter suspended rat, including partial weight bearing (surrogate for artificial gravity) episodic full weight bearing (2 hour/day full weight bearing) and treatment with the third generation bisphosphonate ibandronate (Roche). Graded mechanical loading was studied by housing the animals on a novel servo controlled force plate system which permitted the titration of mechanical force at varying frequency and amplitude and different levels of weight bearing. The force plate, which forms the cage floor, is a glass platform supported by an 18" diameter speaker cone filled with expanding polyurethane foam. An infrared optical sensor attached to the speaker cone yields a voltage linearly related to vertical displacement of the glass platform. The dynamic force on the paw was computed as a product of the apparent mass of the animal on the platform at rest and the acceleration of the platform determined from the second derivative of the optical sensor output. The mass of the animal on the platform was varied by adjusting tension on the tether suspending the animal. Mechanical impact loading was titrated with the force plate resonating at different frequencies, including 3 Hz and 16 Hz.

Long-term alcohol consumption in the rat affects femur cross-sectional geometry and bone tissue material properties.

BACKGROUND: Alcohol consumption previously has been demonstrated to reduce the density and strength of cortical bone of young, actively growing rats. Osteoblast activity and trabecular bone volume were also significantly lower. A germane question arising from these studies is whether the detrimental effects would persist into adulthood. To address this issue, a long-term study was undertaken with animals that consumed alcohol throughout their life and into old age. METHODS: One-month-old female Sprague-Dawley rats were divided into three diet groups: alcohol-fed, pair-fed, and chow-fed. The alcohol-fed animals received a modified Lieber-DeCarli diet that contained 35% ethanol-derived calories. The pair-fed group served as a caloric-equivalent control, and the chow-fed animals served as a completely untreated control. Animals were euthanized after five time periods on the diets that represented three stages of the life span: young (3 months), adult (6, 9, 12 months), and aged (18 months). The left femur was isolated and mechanically tested in 3-point bending for mechanical properties. RESULTS: In the young animals, alcohol consumption produced dramatic reductions in both extrinsic (whole bone) and intrinsic (tissue material) properties, which is consistent with results from previous studies on growing rats. For the adult animals, however, the alcohol groups were only slightly lower and the differences were not statistically significant. The aged animals showed diminished properties due to alcohol, but only for the intrinsic material properties. The extrinsic properties remained similar to controls as a result of greater radial expansion in the femur diaphysis. Despite the cross-sectional areas being the same, this expansion gave rise to higher cross-sectional moment of inertia values in the alcohol animals. The thickness of the cortical wall was lowest in the alcohol group at all time points. CONCLUSIONS: Long-term alcohol consumption produced two major effects in the oldest animals studied: the quality of the cortical bone tissue was diminished, as evidenced by reduced elastic modulus and ultimate strength values, and the bone seemed to compensate for this by expanding the cross-section to produce larger cross-sectional moment of inertia values. The reduced bone tissue quality is consistent with the lower ash percent values in the alcohol animals, but other factors such as the quality of the collagen and mineral crystal may also be important contributors.

Binge drinking and bone metabolism in a young actively growing rat model.

BACKGROUND: Chronic alcohol consumption has been demonstrated to be deleterious to bone health. However, binge drinking is the prevalent form of drinking in young people, which was the impetus for the present study to determine the effect of week-end and week-long binge drinking on bone health in a young actively growing animal model. METHODS: Four-week-old, female, Sprague-Dawley rats were given the amount of 5% alcohol by gavage to be equivalent to a 63 kg woman drinking six beers a day for either 2 or 5 consecutive days per week. RESULTS: There were no changes in the 5-day binge animals, but the 2-day binge animals were hypocalcemic. Similarly, 2-day binge animals had slightly increased bone chemistry and histomorphometric values for both tibia and femur, but only femur length, dry weight, and ash weight as well as femur density, presented either as g/ml or ash weight per unit volume, were increased by a statistically significant level. Cross-section periosteal Mineral Apposition Rate (MAR) was significantly decreased in the 2-day alcohol fed animals. CONCLUSIONS: Actively growing rats given 5% alcohol by gavage for 2 days per week have an increased bone length, bone weight, and bone density. The interpretation of these results must be viewed with great caution because studies of chronic alcohol consumption, and many studies of acute drinking, clearly indicate deleterious effects of alcohol on bone health. Those fed alcohol for 5 days per week showed no change.

Mechanical loading attenuates bone loss due to immobilization and calcium deficiency.

Our purpose was to determine the effects of a mechanical loading intervention on mass, geometry, and strength of rat cortical bone during a period of disuse concurrent with calcium deficiency (CD). Adult female rats were assigned to unilateral hindlimb immobilization, immobilized-loaded, or control (standard chow, 1.85% calcium) treatments. Both immobilized groups were fed a CD rat chow (0.01% calcium) to induce high bone turnover. Three times weekly, immobilized-loaded rats were subjected to 36 cycles of 4-point bending of the immobilized lower leg. After 6 wk, the immobilized rats exhibited decreased tibial shaft bone mineral density (-12%), ultimate load (-19%), and stiffness (-20%; tested in 3-point bending to failure) vs. control rats. Loading prevented this decline in bone density and attenuated decreases in ultimate load and stiffness. Elastic modulus was unaffected by disuse or loading. Bone cross-sectional area in the immobilized-loaded rats was equivalent to that of control animals, even though endocortical resorption continued unabated. On the medial periosteum, percent mineralizing surface doubled vs. that in immobilized rats. This loading regimen stimulated periosteal mineralization and maintained bone mineral density, thereby attenuating the loss in bone strength incurred with disuse and concurrent calcium deficiency.