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  • 1
    Electronic Resource
    Electronic Resource
    Bone Response to In Vivo Mechanical Loading in Two Breeds of Mice (1998)
    Springer
    Calcified tissue international 63 (1998), S. 442-449 
    Details
    ISSN: 1432-0827
    Keywords: Key words:In vivo strain — External loading — Four-point bending — Tibia.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Abstract. We investigated the bone response to external loading in C57BL/6J and C3H/HeJ mice, both breeds with low and high bone density, respectively. An in vivo tibial four-point bending device previously used for application of measured external loads in rats was adapted for mice. It delivered a uniform medio-lateral bending moment to the region of the tibia located 1–5.5 mm proximal to the tibio-fibula junction. The right legs of six C57BL/6J [low bone density (LBD)] and C3H/HeJ [high bone density (HBD)] mice were externally loaded in the device for 36 cycles/day at 2 Hz, 6 days/week for 2 weeks at 9.3 ± 0.9 N force, inducing estimated lateral periosteal surface compressive strains of 5121 ± 1128 με in C3H/HeJ (HBD) mice (n = 6), significantly higher than the estimated 3988 ± 820 με in C57BL/6J mice (n = 6) (mean ± SD). In addition, C3H/HeJ HBD mice (n = 11) were externally sham (pad pressure or no bending) loaded in the device for 36 cycles/day at 2 Hz, 3 days/week for 3 weeks at 9.3 ± 0.9 N force. Calcein injections for bone labeling were given at the 10th and 3rd days before sacrifice. At the end of the experiment, all mice were killed and both tibiae were removed, fixed, embedded, and cross-sectioned through the loaded region. Both tibiae were measured for marrow area (Ma.Ar), cortical area (Ct.Ar), total area (Tt.Ar), cross-sectional moment of inertia (CSMI), and periosteal and endocortical woven bone surface (Wo.B/BS), single-labeled surface (sLS), double-labeled surface (dLS), and total formation surface (FS/BS). Differences in all variables due to breed and loading (both bending and sham-bending) were tested by two-way analysis of variance (ANOVA) (P 〈 0.05). Ma.Ar, Tt.Ar, and CSMI were greater in C57BL/6J (LBD) than in C3H/HeJ (HBD) mice. Periosteal and endocortical woven bone and formation surface were increased significantly more by loading (bending) in C57BL/6J than in C3H/HeJ mice. Periosteal woven bone response due to sham-bending or sham-loading was significantly lower than due to bending loads in the C3H/HeJ mice. We conclude that the bone response to external loading is greater in LBD mice than in HBD mice. The high bone density of C3H/HeJ (HBD) mice is related to breed-specific factors other than the response to loading.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002239900554
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  • 2
    Electronic Resource
    Electronic Resource
    Genetic Variations in Bone Density, Histomorphometry, and Strength in Mice (2000)
    Springer
    Calcified tissue international 67 (2000), S. 337-344 
    Details
    ISSN: 1432-0827
    Keywords: Key words: BL6, DBA, C3H mice — Density — Alkaline phosphatase — Bone strength — Bone formation rate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Abstract. The purpose of this study was to assess breed-related differences in bone histomorphometry, bone biomechanics, and serum biochemistry in three mouse breeds shown to differ in bone mineral density (BMD) (as measured by DXA) and bone mineral content (BMC). Femurs, tibiae, and sera were collected from 16-week-old C3H/HeJ {C3H}, C57BL/6J {BL6}, and DBA/2J {DBA}mice (n = 12/breed). Data collected included BMC and BMD (femora), histomorphometry of cancellous (distal femur) and cortical bone (diaphyseal tibiae and femora), bone strength (femora), and serum alkaline phosphatase (ALP). Consistent with previous reports, BMC and BMD were higher in C3H than in BL6 or DBA mice. The higher BMD in the C3H breed was associated with greater cancellous bone volume, cortical bone area, periosteal bone formation rate, biomechanical strength, and serum ALP. However, mid-diaphyseal total femoral and tibial cross-sectional area and moment of inertia were greatest in BL6, intermediate in C3H, and lowest in DBA mice. The specific distribution of cortical bone in C3H, BL6, DBA mice represents a difference in adaptive response to similar mechanical loads in these breeds. This difference in adaptive response may be intrinsic to the adaptive mechanism, or may be intrinsic to the bone tissue material properties. In either case, the bone-adaptive response to ordinary mechanical loads in the BL6 mice yields bones of lower mechanical efficiency (less stiffness per unit mass of bone tissue) and does not adapt as well as that of the C3H mice where the final product is a bone with greater resistance to bending under load. We suggest that the size, shape, and BMD of the bone are a result of breed-specific genetically regulated cellular mechanisms. Compared with the C3H mice, the lower BMD in BL6 mice is associated with long bones that are weaker because the larger cross-sectional area fails to compensate completely for their lower BMD and BMC.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002230001144
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  • 3
    Electronic Resource
    Electronic Resource
    Bone Mineral Density and Turnover Following Forelimb Immobilization and Recovery in Young Adult Dogs (1996)
    Springer
    Calcified tissue international 59 (1996), S. 401-406 
    Details
    ISSN: 1432-0827
    Keywords: Key words: Bone mineral density — Cancellous bone — Cortical bone.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Abstract. The purpose of this experiment was to study changes in bone mass, structure, and turnover in the canine forelimb after unilateral immobilization and recovery. The right forelimbs of 14 adult mongrel dogs were immobilized for 16 weeks. Six dogs served as controls. Seven immobilized and three control dogs were euthanized at the end of the immobilization period. Recovery consisted of 16 weeks of kennel confinement followed by 16 weeks of treadmill exercise. Seven once-immobilized and three control dogs were euthanized at the end of the recovery period. Bone mineral density of both the proximal (PBMD) and central (CBMD) radius was determined by dual X-ray absorptiometry. Standard histomorphometric endpoints for bone mass and turnover were determined in the cancellous bone of the proximal radius. After immobilization, PBMD, CBMD, and trabecular thickness were lower in the immobilized limb than in either the contralateral or control limbs (P 〈 0.05). Only CBMD remained significantly lower (P 〈 0.05) after recovery. At the end of immobilization, bone formation endpoints were significantly higher in the immobilized limb than both the contralateral and control limbs. Bone turnover was also significantly lower in the contralateral limb than in the immobilized and control limbs. After recovery, all differences in bone turnover had resolved. Immobilization of 16 weeks duration caused an elevation in cancellous bone formation rate and reduced bone density in both cortical and cancellous bone. After 32 weeks of recovery, turnover abnormalities disappeared, cancellous bone normalized, but cortical bone mass remained low. Recovery of cortical bone from immobilization takes longer than recovery of cancellous bone.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002239900147
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  • 4
    Electronic Resource
    Electronic Resource
    Bone Response to In Vivo Mechanical Loading in C3H/HeJ Mice (1999)
    Springer
    Calcified tissue international 65 (1999), S. 41-46 
    Details
    ISSN: 1432-0827
    Keywords: Key words: Strain — External loading — Four-point bending — Tibia — Histomorphometry — C3H/HeJ mice.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Abstract. Bone, being sensitive to mechanical stimulus, adapts to mechanical loads in response to bending or deformation. Although the signal/receptor mechanism for bone adaptation to deformation is still under investigation, the mechanical signal is related to the amount of bone deformation or strain. Adaptation to changes in physical activity depends on both the magnitude of increase in strain above average daily levels for maintaining current bone density and the Minimum Effective Strain (MES) for initiating adaptive bone formation. Given the variation of peak bone density that exists in any human population, it is likely that variation in levels for MES is, to a considerable degree, inherited and varies among animal species and breeds. This study showed a dose-related periosteal response to loading in C3H/HeJ mice. The extent of active formation surface, the rate of periosteal bone formation, and area of bone formation increased with increasing peak periosteal strain. In these mice, the loaded tibia consistently showed lower endocortical formation surface and mineral apposition rate than the nonloaded bones at every load level. Although periosteal expansion is the most efficient means of increasing moment of inertia in adaptation to bending, a dose response increase in endocortical formation would have been predicted. Our characterization of the mouse bone formation response to increasing bending loads will be useful in the design of experiments to study the tibial adaptive response to known loads in different mouse breeds.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002239900655
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  • 5
    Electronic Resource
    Electronic Resource
    On animal models for studying bone adaptation (1994)
    Springer
    Calcified tissue international 55 (1994), S. 316-318 
    Details
    ISSN: 1432-0827
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00310412
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  • 6
    Electronic Resource
    Electronic Resource
    Mechanical loading stimulates rapid changes in periosteal gene expression (1994)
    Springer
    Calcified tissue international 55 (1994), S. 473-478 
    Details
    ISSN: 1432-0827
    Keywords: Strain ; Rat tibia ; c-fos ; Alkaline phosphatase ; Osteocalcin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Abstract Although mechanical forces regulate bone mass and morphology, little is known about the signals involved in that regulation. External force application increases periosteal bone formation by increasing surface activation and formation rate. In this study, the early tibial periosteal response to external loads was compared between loaded and nonloaded contralateral tibia by examining the results of blot hybridization analyses of total RNA. To study the impact of external load on gene expression, RNA blots were sequentially hybridized to cDNAs encoding the protooncogene c-fos, cytoskeletal protein β-actin, bone matrix proteins alkaline phosphatase (ALP), osteopontin (Op), and osteocalcin (Oc), and growth factors insulin-like growth factor I (IGF-I) and transforming growth factor-β (TGF-β). The rapid yet transient increase in levels of c-fos mRNA seen within 2 hours after load application indirectly suggests that the initial periosteal response to mechanical loading is cell proliferation. This is also supported by the concomitant decline in levels of mRNAs encoding bone matrix proteins ALP, Op, and Oc, which are typically produced by mature osteoblasts. Another early periosteal response to mechanical load appeared to be the rapid induction of growth factor synthesis as TGF-β and IGF-I mRNA levels were increased in the loaded limb with peak levels being observed 4 hours after loading. These data indicate that the acute periosteal response to external mechanical loading was a change in the pattern of gene expression which may signal cell proliferation. The altered pattern of gene expression observed in the present study supports previous evidence of increased periosteal cell proliferation seen both in vivo and in vitro following mechanical loading.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00298562
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  • 7
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    Morphometry of bone cell nuclei and their location relative to bone surface (1984)
    Institute of Physics
    Details
    Publication Date: 1984-08-01
    Print ISSN: 0031-9155
    Electronic ISSN: 1361-6560
    Topics: Biology , Medicine , Physics
    Published by Institute of Physics
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    PAPER CURRENT
  • 8
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    Prostaglandin E2 increases the skeletal response to mechanical loading (1997)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Description: The study tested the influence of prostaglandin E2 (PGE2) on the skeletal response to increased in vivo mechanical loading through a four-point bending device. One hundred and twenty Sprague-Dawley female rats (6 months old, 354 +/- 34 g) were divided into 12 groups to accommodate all possible combinations of doses of loads (25, 30, or 35 N) and PGE2 (0, 0.1, 0.3, or 1 mg/kg). Rats received subcutaneous injections of PGE2 daily and in vivo loading of the right tibia every Monday, Wednesday, and Friday for four weeks. Histomorphometric analysis of the periosteal and endocortical surfaces following in vivo dual fluorochrome labeling was performed on both the loaded region of the right tibial diaphysis and a similar region of the left tibial diaphysis. Without PGE2, the threshold for loading to stimulate bone formation was 30 N (peak strain 1360 mu epsilon) at the periosteal surface and 25 N (peak strain 580 mu epsilon) at the endocortical surface. Without loading, the minimum dose of PGE2 to stimulate bone formation at all surfaces was 1 mg/kg/day. When 1 mg/kg/day PGE2 was combined with the minimum effective load, an additive effect of PGE2 and loading on bone formation was observed at the endocortical surface, but a synergistic effect was noted at the periosteal surface. No combined effect of ineffective doses of loading and PGE2 was found. A synergistic effect at peak strains of approximately 1625 mu epsilon on the periosteal surface could suggest either the involvement of locally produced growth factors or autoregulation of endogenous synthesis of PGE2 by exogenously administered PGE2.
    Keywords: Aerospace Medicine
    Type: Journal of bone and mineral research : the official journal of the American Society for Bone and Mineral Research (ISSN 0884-0431); Volume 12; 2; 276-82
    Format: text
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    NASA TECHNICAL REPORTS
  • 9
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    Experiment K305: Quantitative analysis of selected bone parameters. Supplement 2: Bone elongation rate and bone mass in metaphysis of long bones (1981)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: The proximal humeral metaphysis of rats from time periods recovery plus zero days (R+0), recovery plus six days (R+6), and recovery plus twenty nine days (R+29) was analyzed. The volume of calcified cartilage and bone in flight and synchronous controls was reduced in groups R+0 and R+6, but was normal in group R+29. The number of functional bone cells (osteoblasts and osteoclasts) was decreased in proportion to the amount of bone in the early groups, and was normal in the last group. The fatty marrow volume was increased only in flight animals of groups R+0 and R+6, but was normal in the R+29 group. Accumulation of excess fatty marrow was seen only in flight animals. The decreased amount of bone and calcified cartilage is believed to be the result of a temporarily slowed or arrested production of calcified cartilage as a substrate for bone formation. This would have resulted from slowed bone elongation during flight and synchronous control conditions. Bone elongation returned to normal by twenty nine days after return.
    Keywords: LIFE SCIENCES (GENERAL)
    Type: NASA. Ames Research Center US Rat Expts. Flown on the Soviet Satellite Cosmos 1129; p 149-175
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    NASA TECHNICAL REPORTS
  • 10
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    Effects of spaceflight on trabecular bone in rats (1983)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Alterations in trabecular bone were observed in growing male Wistar rats after 18.5 days of orbital flight on the COSMOS 1129 biosatellite. Spaceflight induced a decreased mass of mineralized tissue and an increased fat content of the bone marrow in the proximal tibial and humeral metaphyses. The osteoblast population appeared to decline immediately adjacent to the growth cartilage-metaphyseal junction, but osteoclast numbers were unchanged. These results suggested that bone formation may have been inhibited during spaceflight, but resorption remained constant. With the exception of trabecular bone mass in the proximal tibia, the observed skeletal changes returned to normal during a 29-day postflight period.
    Keywords: LIFE SCIENCES (GENERAL)
    Type: American Journal of Physiology: Regulatory, Interactive and Comparative Physiology (ISSN 0363-6119); 13; March 19
    Format: text
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    NASA TECHNICAL REPORTS
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