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Purpose: A short period of disuse of 1-2 weeks due to factors such as illness or injury can lead to muscle atrophy, affecting both athletic performance and health. Recent research has shown that uridine 5'-monophosphate (5'-UMP) can counteract disuse-induced muscle atrophy by increasing PGC-1α expression and inhibiting atrogin-1 expression. However, the effect of 5'-UMP on disuse muscle atrophy in humans remains unknown. Therefore, the aimed of this study was to explore the effects of 5'-UMP supplementation during detraining on short-term disuse muscle atrophy in healthy men. Methods: Following a 6-week resistance training program on upper arm, healthy men were randomized to either a UMP group (n = 11) or a placebo group (n = 10), taking their respective supplements during the 2-week detraining period. Muscle thickness, an indicator of muscle hypertrophy and atrophy, was measured at 3 positions (MT50, MT60, and MT70) at baseline, 1 week, and 2 weeks after detraining. Results: Both groups showed a significant decrease in muscle thickness at MT70. The relative decrease was greater in the placebo group (2.4 ± 2.8%) than in the UMP group (0.0 ± 2.0%), significantly (p = 0.034) at 1 week. However, no significant difference was observed at MT50 and MT60. Conclusion: After the hypertrophy, 5'-UMP may prevent muscle atrophy due to the detraining within the first week.
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Objectives: The objective is to compare stiffness changes around the shoulder muscles between pitchers and position players after throwing overhead using shear wave elastography (SWE) in relation to throwing motion analysis and muscle strength. Methods: A total of 32 male college baseball players (12 pitchers and 20 position players) were observed throwing 20 times, and SWE was performed to evaluate 13 shoulder muscle items-tendons (supraspinatus, infraspinatus, subscapularis, and teres minor), muscles (supraspinatus, infraspinatus [transverse and oblique part], teres minor, lower trapezius, latissimus dorsi, and pectoralis minor), and capsules (posterior and posteroinferior). Motion analysis was used to assess elbow torque, forearm angle, forearm rotation speed, and maximum external rotation angle of the shoulder. Muscle strength was measured using a dynamometer for abduction, internal/external rotation of the shoulder at an abduction of 0°, internal/external rotation of the shoulder at an abduction of 90°, and internal/external rotation of shoulder at a flexion of 90°. Results: In the pitcher group, SWE values for the teres minor muscle and latissimus dorsi muscle increased significantly after throwing. In the position player group, SWE values for the teres minor muscle significantly increased, and SWE values of the pectoralis minor muscle decreased after throwing. In the pitcher group, positive correlations were found between the teres minor muscle and forearm rotation speed and between the latissimus dorsi muscle and forearm angle. No significant difference was found in muscle strength after throwing in any of the groups. Conclusions: Stiffness changes occurred after throwing and were related to the motion analysis, but the regions in which stiffness occurred varied between pitchers and position players.
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A novel scanning protocol, ammonite scan, is proposed for widefield optical coherence tomography angiography (OCTA) and relative retinal blood flow velocity imaging in the human retina using variable interscan time analysis (VISTA). A repeated circle scan using a 400 kHz swept-source was employed to achieve an interscan time of 1.28â ms. The center of the repeated circular scan continuously moved spirally towards the peripheral region, ensuring an extended and adjustable scan range while preserving the short interscan time. Image artifacts due to eye movement were eliminated via extra motion-correction processing using data redundancy. The relative blood flow velocity in superficial and deep plexus layers was calculated from the VISTA image, and their ratio was used to explore the microvascular flow parameter in the healthy human eye.
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Post-transcriptional modifications of tRNA are crucial for their core function. The inosine (I; 6-deaminated adenosine) at the first position in the anticodon of tRNAArg(ICG) modulates the decoding capability and is generally considered essential for reading CGU, CGC, and CGA codons in eubacteria. We report here that the Bacillus subtilis yaaJ gene encodes tRNA-specific adenosine deaminase and is non-essential for viability. A ß-galactosidase reporter assay revealed that the translational activity of CGN codons was not impaired in the yaaJ-deletion mutant. Furthermore, tRNAArg(CCG) responsible for decoding the CGG codon was dispensable, even in the presence or absence of yaaJ. These results strongly suggest that tRNAArg with either the anticodon ICG or ACG has an intrinsic ability to recognize all four CGN codons, providing a fundamental concept of non-canonical wobbling mediated by adenosine and inosine nucleotides in the anticodon. This is the first example of the four-way wobbling by inosine nucleotide in bacterial cells. On the other hand, the absence of inosine modification induced +1 frameshifting, especially at the CGA codon. Additionally, the yaaJ deletion affected growth and competency. Therefore, the inosine modification is beneficial for translational fidelity and proper growth-phase control, and that is why yaaJ has been actually conserved in B. subtilis.
Subject(s)
Anticodon , Magnoliopsida , Adenosine Deaminase/genetics , Bacillus subtilis/genetics , RNA, Transfer, Arg , RNA, Transfer/genetics , Adenosine/genetics , Inosine/geneticsABSTRACT
PURPOSE: To investigate shoulder stiffness on the throwing and non-throwing sides in college baseball players using ultrasound shear wave elastography (SWE), and investigate the relationship between stiffness and shoulder pain during throwing. METHODS: Forty-nine college baseball players (98 shoulders) were recruited. Shoulder range of motion was evaluated. SWE was used to measure stiffness of the bilateral supraspinatus tendons, infraspinatus tendons, subscapularis tendons, supraspinatus muscles, infraspinatus muscles (ISPM), and posterior capsules. Participants were divided into pain and no pain groups based on the presence or absence of shoulder pain during throwing within 1 month before measurements on the throwing side. Items were compared between the throwing and non-throwing sides, and between the pain and no pain groups. Factors affecting shoulder pain during throwing were also investigated via multiple logistic regression analysis. RESULTS: Compared with the non-throwing side, the throwing side had significantly greater external rotation at 90° abduction, significantly lesser internal rotation at 0° abduction and internal rotation at 90° abduction (AbdIR), significantly higher SWE values of the infraspinatus tendon, ISPM, and posterior capsule, and significantly lower SWE values of the subscapularis tendon. Compared with the no pain group, the pain group had a significantly higher SWE value of the ISPM, and significantly lesser AbdIR. Increased ISPM SWE values and decreased AbdIR were significantly correlated with shoulder pain during throwing. CONCLUSIONS: The posterior tissue was stiffer than the anterior tissue on the throwing side. Decreased AbdIR and increased ISPM stiffness may be correlated with shoulder pain during throwing.
Subject(s)
Baseball , Elasticity Imaging Techniques , Shoulder Joint , Humans , Shoulder/diagnostic imaging , Shoulder Pain , Shoulder Joint/diagnostic imaging , Baseball/physiology , Range of Motion, Articular/physiologyABSTRACT
Objectives: This study aimed to determine the effects of high-intensity isokinetic training with blood flow restriction during rest interval between set (rBFR) versus during exercise (eBFR) on muscle hypertrophy and increasing muscle strength and determine whether BFR-induced exercise pain is suppressed by rBFR. Materials and Methods: Fourteen arms (7 participants) were recruited for the study. We conducted the following interventions for each arm: eBFR (n=4), rBFR (n=5), and exercise only (CON, n=5). The participants performed elbow flexion training with a BIODEX device twice weekly for 8 weeks. This study training consisted of total four sets; each was performed until <50% peak torque was achieved twice consecutively. BFR pressure was set at 120 mmHg. Elbow flexor peak torque during concentric contraction (CC), isometric contraction (IM), and muscle cross-sectional area (CSA) were measured before and after the intervention. Numerical rating scale scores used to assess pain during exercise were determined during training. Results: Peak torque at the CC increased in the rBFR (p<0.05) and IM increased in the rBFR and CON (p<0.05), while CSA increased in the rBFR and CON (p<0.001). The pain during exercise was severe in the eBFR and moderate in the rBFR and CON. Conclusions: This study's showed that high-intensity isokinetic training with rBFR did not have a synergistic effect on increasing muscle strength and muscle size. Additionally, high-intensity isokinetic training with BFR when it may be best not to perform it during exercise, because it was induces severe pain and may inhibit increases in muscle strength.
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PURPOSE: We assessed the effects of low-intensity exercise with blood flow restriction (BFR) during rest intervals on recovery of muscle function and pain during exercise and rest intervals. METHODS: Participants were 10 males and study arms of the participants were randomly assigned into three conditions; low-intensity exercise with BFR during rest intervals (rBFR), low-intensity exercise with BFR during exercise (eBFR) and low-intensity exercise only (EO). The exercise task was elbow flexion until repetition failure at 30% of 1 RM and cuff pressure was 120 mmHg. The maximum voluntary isometric contraction (MVIC) and the muscle endurance (ME) were measured pre, post, 1, 24 and 48 h after the exercise. Pain during exercise and rest intervals were evaluated using the Numerical Rating Scale. RESULTS: MVIC and ME significantly decreased after exercise in all conditions. Pain during exercise was lower in rBFR (4.2 ± 2.9) (p = 0.007) and EO (4.4 ± 2.7) (p = 0.014) conditions compared to eBFR condition (6.7 ± 1.7), but the pain during rest intervals was more intense in rBFR condition (5.2 ± 1.6) compared to eBFR (1.5 ± 1.4) and EO (1.7 ± 1.2) conditions (p < 0.001). CONCLUSION: We discovered that recovery of muscle function was the same as BFR during rest intervals and BFR during exercise. Also, our results suggested that BFR itself may cause the perception of pain. Future studies are thus required to investigate the optimal dosage focusing on the pressure volume and intensity used in BFR during intervals.
Subject(s)
Resistance Training , Humans , Male , Muscle, Skeletal/blood supply , Pain , Perception , Regional Blood Flow/physiology , Resistance Training/methodsABSTRACT
Physical inactivity impairs muscle insulin sensitivity. However, its mechanism is unclear. To model physical inactivity, we applied 24-h hind-limb cast immobilization (HCI) to mice with normal or high-fat diet (HFD) and evaluated intramyocellular lipids and the insulin signaling pathway in the soleus muscle. Although 2-wk HFD alone did not alter intramyocellular diacylglycerol (IMDG) accumulation, HCI alone increased it by 1.9-fold and HCI after HFD further increased it by 3.3-fold. Parallel to this, we found increased protein kinase C ε (PKCε) activity, reduced insulin-induced 2-deoxyglucose (2-DOG) uptake, and reduced phosphorylation of insulin receptor ß (IRß) and Akt, key molecules for insulin signaling pathway. Lipin1, which converts phosphatidic acid to diacylglycerol, showed increase of its activity by HCI, and dominant-negative lipin1 expression in muscle prevented HCI-induced IMDG accumulation and impaired insulin-induced 2-DOG uptake. Furthermore, 24-h leg cast immobilization in human increased lipin1 expression. Thus, even short-term immobilization increases IMDG and impairs insulin sensitivity in muscle via enhanced lipin1 activity.NEW & NOTEWORTHY Physical inactivity impairs muscle insulin sensitivity. However, its mechanism is unclear. To model physical inactivity, we applied 24-h hind-limb cast immobilization to mice with normal or high-fat diet and evaluated intramyocellular lipids and the insulin signaling pathway in the soleus muscle. We found that even short-term immobilization increases intramyocellular diacylglycerol and impairs insulin sensitivity in muscle via enhanced lipin1 activity.
Subject(s)
Diglycerides/metabolism , Insulin Resistance , Muscle, Skeletal/metabolism , Phosphatidate Phosphatase/metabolism , Sedentary Behavior , Adult , Animals , Casts, Surgical , Hindlimb Suspension , Humans , Insulin/metabolism , Insulin Resistance/physiology , Male , Mice , Mice, Inbred C57BL , Muscle, Skeletal/pathology , Signal Transduction/physiology , Time Factors , Young AdultABSTRACT
High lateral resolution (â¼5µm) optical coherence tomography (OCT) that employs a variable cross-cylinder (VCC) to compensate for astigmatism is presented for visualizing minute structures of the human retina. The VCC and its sensorless optimization process enable ocular astigmatism correction of up to -5.0 diopter within a few seconds. VCC correction has been proven to increase the signal-to-noise ratio and lateral resolution using a model eye. This process is also validated using the human eye by visualizing the capillary network and human cone mosaic. The proposed method is applicable to existing OCT, making high lateral resolution OCT practical in clinical settings.
Subject(s)
Astigmatism/therapy , Retina/diagnostic imaging , Tomography, Optical Coherence/methods , Computer Systems , HumansABSTRACT
PURPOSE: Muscle mass is known to rapidly decrease with muscle disuse. Previous reports suggest that repetitive blood flow restriction (BFR) mitigates the reduction of muscle mass with disuse. However, the effects of BFR on muscle atrophy and gene expression levels in muscle during cast immobilization have not been clarified. METHODS: To investigate the effect of BFR on muscle atrophy and gene expression levels during cast immobilization in humans, we recruited 10 healthy males who were randomly divided into the control and BFR treatment groups. All subjects were immobilized with a cast for 14 days. BFR treatment was conducted only in the BFR group. We evaluated cross sectional area (CSA) of thigh muscles by magnetic resonance imaging before and 14 days after cast immobilization. A percutaneous biopsy of the vastus lateralis muscle (VL) was performed before and 1, 7, and 14 days after cast immobilization. Expression of genes related to muscle atrophy and synthesis were evaluated using real-time PCR. RESULTS: The CSA of the VL and the thigh flexor muscles were significantly decreased in both groups; however, percent decrease in CSA was significantly smaller in the BFR group compared with the control group. In two-way repeated ANOVA analysis, the time × treatment interaction in gene expression of the muscle-specific ubiquitin ligases muscle ring finger 1 (MuRF1) was significant, and elevated MURF1 expression level by cast immobilization was seemed to be suppressed by the BFR treatment. CONCLUSION: BFR treatment may prevent reduced VL and thigh flexor muscles and increased MuRF1 expression level during cast immobilization. Further study is required to confirm these results.
Subject(s)
Quadriceps Muscle/blood supply , Quadriceps Muscle/physiology , Adult , Blood Circulation/physiology , Gene Expression Regulation , Humans , Immobilization/methods , Male , Muscle Proteins/genetics , Muscle Proteins/metabolism , Muscle Strength/physiology , Muscular Atrophy/metabolism , Muscular Atrophy/pathology , Pilot Projects , Quadriceps Muscle/anatomy & histology , Quadriceps Muscle/metabolism , Tripartite Motif Proteins/genetics , Tripartite Motif Proteins/metabolism , Ubiquitin-Protein Ligases/genetics , Ubiquitin-Protein Ligases/metabolism , Young AdultABSTRACT
Introduction: One reason athletes train their trunk muscles is that the body's trunk stability has been shown to prevent injury. However, the relationship between body trunk muscle thickness, particularly that of deep muscles, and athletic performance remains to be clarified. Purpose: We aimed to explore the relationship between 100-m sprint performance and the sizes of the trunk stabilizing muscles, the psoas major muscle (PM), transversus abdominis (TA), and multifidus muscle (MM), in collegiate sprinters. Methods: Fourteen male sprinters belonging to a university athletics club participated in this study. The thicknesses of the TA and MM were measured using an ultrasonic diagnostic apparatus (ProSound C3; Aloka, Tokyo, Japan). The cross-sectional area of the PM was assessed by a magnetic resonance imaging apparatus (Vantage Elan; Toshiba Medical Systems, Tokyo, Japan). The relationship between these anthropometric parameters and the 100-m sprint time was analyzed by Spearman's correlation coefficient, multi- regression analysis, and the change-point regression model. Results: The sizes (mean ± SD) of the muscles were: PM, 43.074 ± 7.35 cm2; TA, 4.36 ± 0.72 mm; and MM, 3.99 ± 0.48 cm. The mean 100-m sprint time was 11.00 ± 0.48 s. Spearman's correlation analysis revealed that the 100-m sprint time had a significant moderate negative correlation with TA (ρ = -0.691, p < 0.01) and a low negative but not significant correlation with MM (ρ = -0.327, p = 0.28), whereas PM did not show a significant or in-negligible correlation. The change-point regression model found the change-points in the 100-m sprint time and the thickness of the TA and MM at 4.70 mm (95% CI: 4.00-5.43 mm) and 3.84 cm (95% CI: 3.28-4.31 cm), respectively. The sprint time decreased with an increase in the thickness of the muscles up to the change-points, whereas it did not change even if the muscles became thicker than the change-points. The change-points were consistently observed when the thickness of the muscles was normalized by body mass. Conclusion: Sprint performance for 100-m was found to be associated with TA and MM thickness in a biphasic manner. As muscle thickness increased, the sprint time decreased, followed by a plateau phase.
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This study aimed to examine the effects of batting practice and visual training focused on the pitch type and speed on batting ability and visual function. A total of 46 participants took part in 12 training sessions for 4 weeks. The participants were divided into six groups according to the training type as follows: Group 1, batting practice with a fastball at 100 km/h; Group 2, tracking (watching) a fastball at 100 km/h; Group 3, batting practice with a fastball at 115 km/h; Group 4, tracking a fastball at 115 km/h; Group 5, batting practice with a curve ball at 100 km/h; and Group 6, tracking a curve ball at 100 km/h. Dynamic visual acuity, depth perception, hand-eye coordination, and batting ability were measured before and after training. Group 1 showed significant improvement in batting ability in the tests with 100 km/h fastballs and curve balls, while Groups 3 and 5 showed significant improvement in batting ability with 100 km/h fastballs and curve balls, respectively. Group 6 also showed significant improvement in batting ability with 100 km/h fastballs. Moreover, Groups 2 and 4 showed significant improvement in Dynamic visual acuity and hand-eye coordination, respectively. The results of the present study suggest that batting practice and visual training improve batting ability for the same pitch types and speeds as those encountered in practice. Therefore, visual training may be an effective method for improving batting ability and visual function in coaching settings.
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[Purpose] This study aimed to clarify the effects and to verify the efficacy of various breathing exercises performed while sitting on a small foam roller on the contraction of pelvic floor muscles in males. [Participants and Methods] This study, involving 10 healthy males (age 19.9 ± 1.6â years), had a crossover design and involved two conditions: sitting at rest for 10â min (CON condition) and sitting on a small foam roller placed on a chair while performing seven breathing exercises (EXE condition). Movement of the posterior side of the bladder was examined in both conditions using ultrasonic imaging. Pelvic floor muscle contraction was evaluated based on the movement distance. [Results] No significant difference was found in any parameter for CON conditions. The distance of bladder posterior side movement was 5.58 ± 2.51â mm (pre), 13.66 ± 5.16â mm (post), and 9.59 ± 3.67â mm (post-1 month) for EXE conditions. Subjective evaluation also demonstrated that the feeling of contraction was stronger immediately after the experiment. [Conclusion] Results demonstrated that various breathing exercises, performed while sitting on a small foam roller, enhanced the voluntary contraction of pelvic floor muscles in males. Efficacy was demonstrated, at least in young males.
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To investigate the effects of a single high-load (80% of one repetition maximum [1RM]) set with additional drop sets descending to a low-load (30% 1RM) without recovery intervals on muscle strength, endurance, and size in untrained young men. Nine untrained young men performed dumbbell curls to concentric failure 2-3 days per week for 8 weeks. Each arm was randomly assigned to one of the following three conditions: 3 sets of high-load (HL, 80% 1RM) resistance exercise, 3 sets of low-load [LL, 30% 1RM] resistance exercise, and a single high-load (SDS) set with additional drop sets descending to a low-load. The mean training time per session, including recovery intervals, was lowest in the SDS condition. Elbow flexor muscle cross-sectional area (CSA) increased similarly in all three conditions. Maximum isometric and 1RM strength of the elbow flexors increased from pre to post only in the HL and SDS conditions. Muscular endurance measured by maximum repetitions at 30% 1RM increased only in the LL and SDS conditions. A SDS resistance training program can simultaneously increase muscle CSA, strength, and endurance in untrained young men, even with lower training time compared to typical resistance exercise protocols using only high- or low-loads.
Subject(s)
Muscle Strength/physiology , Muscle, Skeletal/anatomy & histology , Muscle, Skeletal/physiology , Physical Endurance/physiology , Resistance Training/methods , Weight Lifting/physiology , Adaptation, Physiological , Adult , Arm/physiology , Humans , Isometric Contraction/physiology , Male , Pilot ProjectsABSTRACT
In this study, we aim to clarify the influence based on bone resorption markers at onset of stress fracture. Also, we will clarify the state of the bone resorption markers of female long distance runners who have a history of stress fracture and also ones who routinely practices running long distances. Participants comprised 19 female long distance athletes. The survey period was 2011-2014, and we measured u-NTX as a bone resorption marker at least twice a year, taking the mean±SD of the periodic measured values without stress fracture as the mean value. Measurements were collected sample when stress fractures developed. 132 u-NTX measurements were taken from 19 participants. As a result, the average was 41.03±12.31 nmolBCE/mmolCRE (Q1: 33.15, Q2: 40.55, Q3: 47.95). In six of the 19 participants, u-NTX could be measured following a stress fracture. The mean value of u-NTX for those participants was 40.16±9.10 nmolBCE/mmolCRE, increasing to 64.08±16.07 nmolBCE/mmol CRE with the stress fracture (p<0.01). The findings showed that, in adult female long distance runners, u-NTX values when there was no stress fracture were within the standard value for mean premenopausal women, but increased when the athletes suffered from a stress fracture.
Subject(s)
Athletic Injuries/diagnosis , Bone Resorption , Collagen Type I/analysis , Fractures, Stress/diagnosis , Peptides/analysis , Running/injuries , Adult , Athletes , Biomarkers/analysis , Female , Humans , Young AdultABSTRACT
The maxillary sinus augmentation procedure has become a predictable treatment to regenerate bone for implant placement. The purpose of this study was to evaluate the effect of recombinant human platelet-derived growth factor BB (rhPDGF-BB) combined with a deproteinized cancellous bovine bone graft for sinus augmentation. The lateral window approach was used for maxillary sinuses with minimal residual bone. After a healing period of 4 months, dental implants were placed and then restored following a 2-month osseointegration period. The result demonstrated increased bone height and ISQ values and a 100% survival rate. This study indicates that the addition of rhPDGF-BB to deproteinized cancellous bovine bone accelerated the healing period in maxillary sinuses with minimal native bone.
Subject(s)
Maxilla/surgery , Maxillary Sinus/surgery , Proto-Oncogene Proteins c-sis/therapeutic use , Sinus Floor Augmentation/methods , Adult , Aged , Animals , Becaplermin , Bone Regeneration , Bone Transplantation/methods , Cattle , Dental Implantation, Endosseous , Dental Implants , Female , Humans , Male , Maxilla/diagnostic imaging , Maxillary Sinus/diagnostic imaging , Membranes, Artificial , Middle Aged , Minerals/therapeutic use , Oral Surgical Procedures, Preprosthetic/methods , Osseointegration , Osteotomy , Treatment OutcomeABSTRACT
[Purpose] The purpose of this study was to verify the effects of the long-term care prevention project and develop an effective program. [Subjects] A total of 81 elderly people (age, 79 ± 5.1â years; height, 149.2 ± 9.2â cm; weight, 54.2 ± 11.4â kg). [Methods] Grip, knee extension muscular strength, 10â m walking speed, and Timed Up and Go time were measured for evaluation of motor functions, and the "Locomo 25", a 25-question risk assessment questionnaire, was used as the judgment criterion for evaluation of daily life activities, with measurements being taken at the beginning of the project and after three months. [Results] In the motor functions evaluation, significant differences were observed in 10â m walking speed, Timed Up and Go time, and knee extension strength. In the daily life activities evaluation, scores for pain, rising movement, standing movement, indoor walking, outdoor walking, and fear of falling were significantly reduced. In addition, a significant correlation was also observed between motor functions and daily life activities. [Conclusion] The result of this study indicated that the long-term care prevention project is effective in maintaining or improving muscular strength and mitigating pain in the elderly and that it is an effective program for maintaining daily life activities. We were also able to show that it would be effective to develop programs with a low exercise intensity that can be performed on a continuing by the elderly.
ABSTRACT
Sinus augmentation with various bone graft materials may be required in the posterior maxilla. This study compared bone formation in a lateral window sinus augmentation with recombinant human bone morphogenetic protein 2/acellular collagen sponge (rhBMP-2/ACS) combined with Bio-Oss or Bio-Oss graft alone. Patients were assigned to treatment with either rhBMP-2/ACS + Bio-Oss or Bio-Oss alone. After a healing period, bone cores were harvested. Histologic specimens demonstrated that new bone formation was less in those who received rhBMP-2/ACS + Bio-Oss than those with Bio-Oss alone. This study indicated that the addition of rhBMP-2/ACS to Bio-Oss has a negative effect on bone formation.
Subject(s)
Bone Morphogenetic Protein 2/adverse effects , Bone Regeneration/drug effects , Bone Substitutes/pharmacology , Sinus Floor Augmentation/methods , Adult , Aged , Drug Combinations , Female , Humans , Male , Middle Aged , Minerals/pharmacology , Recombinant Proteins , Skin, ArtificialABSTRACT
Repetitive blood flow restriction prevents muscular atrophy and weakness induced by chronic unloading. However, it was unclear which external compressive force for blood flow restriction was optimal to prevent muscular dysfunction. The present study was intended to investigate the effects of repeated muscle blood flow restriction at low pressure on muscular weakness induced by immobilization without weight bearing. Using casts, the left ankles of 11 healthy males were immobilized for 2 weeks. Subjects were instructed to walk using crutches with no weight bearing during the period. Subjects were divided randomly into two groups: a restriction of blood flow (RBF) group (application of external compressive force of 50 mm Hg) and a control (CON) group (no intervention). We measured changes in the muscle strength of the knee extensor-flexor and ankle plantar flexor. The percent changes in knee extensor torque at 60°/s under eccentric contraction in the RBF group were significantly smaller than in the CON group (-12.5±10.7% and -30.1±10.9%, p<0.05). The percent changes in knee flexor torque when performing an eccentric contraction at 60°/s, an isometric contraction, or a concentric contraction at both 60 and 300°/s in the RBF group were significantly smaller than those in the CON group (p<0.05). In conclusion, our results show that repetitive restriction of blood flow with 50 mm Hg cuff pressure to the lower extremity reduces muscular weakness induced by chronic unloading.