Biomedical subjects

J Y Rho

Publications and source records attributed to J Y Rho.

At least 37 records · Page 2Linked to original sources

PubMed2000

Effect of taurine in rat milk on the growth of offspring.

The physiological significance of taurine in milk in the growth of rat pups was investigated. Our results confirmed that taurine was at an exceptionally high concentration in rat milk during the lactational period, especially for the first few days after birth. Pups taking no milk from natural dams but from foster mothers at an advanced lactational period showed a slower growth rate. Intraperitoneal administration of taurine to the foster mothers in the first five days restored this growth retardation. On the other hand, intraperitoneal administration of beta-alanine, a transport antagonist of taurine, to the natural dams through the lactational period induced a slower growth rate of pups. This beta-alanine treatment to dams increased beta-alanine concentration, but did not decrease taurine concentrations in milk, and serum taurine concentration in the pups receiving this milk was elevated. Direct administration of beta-alanine to pups also increased the serum taurine concentrations dose-dependently. Beta-alanine administration to pups significantly decreased [3H]taurine incorporation into all the organs examined, and in contrast. [3H]taurine concentrations in serum and urine were elevated. Thus, beta-alanine inhibited taurine incorporation into cells and accelerated taurine excretion into either urine or milk. Serum IGF-I levels in pups receiving beta-alanine either directly or via their mothers was significantly lower than those in control pups. Cumulatively, taurine ingestion from milk at an early lactational period seems critical for normal growth of rat neonates due to its role in maintaining normal serum IGF-I levels.

Animals↗

PubMed1999

Mechanical and morphological variation of the human lumbar vertebral cortical and trabecular bone.

The nanoindentation technique was used to characterize the variation in the elastic modulus and hardness of human lumbar vertebral cortical and trabecular bone. The elastic modulus (and in most cases, the hardness as well) of axially aligned trabeculae cut in the transverse direction was significantly greater than in other orientations of vertebral cortical and trabecular bone. In all cases, the elastic modulus and hardness of bone in the load-bearing direction was greater than in corresponding bone types cut in the other directions. Scanning electron micrographs of cortical shell revealed the Haversian-like canal systems expected in secondary cortical bone, but it was difficult to differentiate by morphology cortical from trabecular bone in the human lumbar vertebrae.

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PubMed1999

Elastic properties of microstructural components of human bone tissue as measured by nanoindentation.

The elastic properties of several microstructural components of dry human vertebrae (T-12 and L-1) and tibiae have been investigated in the longitudinal and transverse directions using nanoindentation. The largest Young's modulus was that for the interstitial lamellae in the longitudinal direction (25.7 +/- 1.7 GPa). This was followed in decreasing order by osteons in the longitudinal direction (22.4 +/- 1.2 GPa), trabeculae in the longitudinal direction (19.4 +/- 2.3 GPa), an average over osteons and interstitial lamellae in the transverse direction [16.6 +/- 1.1 GPa (it was difficult to microstructurally distinguish osteons from interstitial lamellae in the transverse direction)], and trabeculae in the transverse direction (15.0 +/- 2.5 GPa). An ANOVA statistical analysis revealed that the values all are significantly different (p < 0.05). Since the elastic moduli in the longitudinal direction are all greater than in the transverse, measurable elastic anisotropies exist in the components. The hardnesses also varied among the microstructural components in the range 0.52-0.74 GPa.

Aged↗

PubMed1999

The role of collagen abnormalities in ultrasound and densitometry assessment: In vivo evidence.

There is little information concerning how the mutation of collagen affects bone mineralization and the assessment of bone properties. To estimate these influences, we performed ultrasonic assessments of the calcaneus and bone mineral density (BMD) measurements of the hip and lumbar spine. Females with diseases related to the mutation of collagen [Ehlers-Danlos syndrome (EDS) type III and systemic sclerosis (SSc)] participated in this study. We compared the broadband ultrasound attenuation (BUA and UBI-4), the average transit time through the heel (TTH), and a multiple factor index (UBI-4T) with control subjects matched on age, race, and menstrual status. Both groups of patients had BMD of the spine (L2-L4) within the normal range for their age and sex (for EDS: n = 23, 1.14 +/- 0. 14 g/cm2 and z-score = 0.37; for SSc: n = 15, 0.98 +/- 0.15 g/cm2 and z-score = 0.20). EDS and SSc subjects had lower BMD of the femoral neck (FN) compared with controls (for EDS: 0.91 +/- 0.13 g/cm2, z-score = -0.41, P = 0.025; for SSc 0.67 +/- 0.13 g/cm2, z-score = -0.92, P = 0.006). Subjects with EDS and SSc also had lower BUA values (P = 0.051-0.001) compared with controls. After adjusting for body weight, height, and the level of physical activity, the difference in FN BMD between EDS or SSc and controls became marginal (EDS: P = 0.072; SSc: P = 0.086). However, the significant difference for BUA between subjects and controls remained for EDS (P = 0.008), and disappeared for SSc (0.70) after adjusting for weight, height, level of physical activity, and BMD. These results suggest that the abnormalities of collagen may impact on bone mass measurements differently depending on skeletal site, modality of the assessment, and the source and nature of collagen defects. To determine whether collagen properties influence QUS, proper models in vivo and in vitro should be used.

Absorptiometry, Photon↗

PubMed1999

Variations in the individual thick lamellar properties within osteons by nanoindentation.

The nanoindentation method was used to examine variations in the individual thick lamellar properties within completed secondary osteons as a function of distance from the osteonal center (haversian canal). In general, there is a decline in both elastic modulus and hardness from the center of the osteon outward. Because some of the osteons may have a different general trend than others, an analysis of covariance was also carried out. The overall analysis was highly significant for both elastic modulus and hardness. Also, osteon number was significant as a factor, indicating that there was some difference in the overall thick lamellar properties of the different osteons. An unpaired t-test showed statistically significant differences (p = 0.0005 and 0.0004, respectively) between thick lamellar properties obtained from most of the inner two osteonal lamellae (E = 20.8 +/- 1.3 GPa and H = 0.65 +/- 0.06 GPa) and those from outermost two osteonal lamellae (E = 18.8 +/- 1.0 GPa and H = 0.55 +/- 0.05 GPa). In general, lamellar properties from near to the center of the osteon were greater than those from the outermost osteonal lamella. The mechanical properties of osteons are also significantly lower than those of the interstitial bone (p < 0.0001). The ratio (E1/E2) of the elastic moduli of the outermost osteonal lamella (E1) (considered to be the soft part of the osteons) and that of interstitial bone (E2) was approximately 0.7. These results may have important implications for the mechanical contribution of individual osteons to bone biomechanics.

Elasticity↗

PubMed1999

Effects of drying on the mechanical properties of bovine femur measured by nanoindentation.

Effects of drying on the measurement of mechanical properties of bone by nanoindentation methods have been examined. Tests were conducted to measure the elastic modulus and hardness of two cross-sectional cortical specimens obtained from adjacent areas of bovine femur. One specimen was thoroughly dried in air prior to testing while the other was stored in deionized water. The properties of osteons and interstitial lamellae showed statistically significant differences (p<0.0001) and were therefore investigated separately. Drying was found to increase the elastic modulus by 9.7% for interstitial lamellae and 15.4% for osteons. The hardness was also found to increase by 12.2% for interstitial lamellae and 17.6% for osteons.

Journal Article↗

PubMed1998

Ultrasonic characterisation in determining elastic modulus of trabecular bone material.

The pulse transmission ultrasonic technique is used to characterise the actual pathway and the wavelength dependence in relation to the bone specimen and microstructural dimensions. The average velocity through individual trabecular bone is 2901 m s-1 (SD 161), and the mean velocity through cylindrical cancellous bone specimens is 2717 m s-1 (SD 171). Thus, the velocity through cylindrical cancellous bone specimens is underestimated by as much as 6.4% of that through individual trabeculae. There is a statistically significant difference in the ultrasonic velocity between individual trabeculae and cylindrical cancellous bone specimens (p = 0.0012).

Bone and Bones↗

PubMed1998

Mechanical properties and the hierarchical structure of bone.

Detailed descriptions of the structural features of bone abound in the literature; however, the mechanical properties of bone, in particular those at the micro- and nano-structural level, remain poorly understood. This paper surveys the mechanical data that are available, with an emphasis on the relationship between the complex hierarchical structure of bone and its mechanical properties. Attempts to predict the mechanical properties of bone by applying composite rule of mixtures formulae have been only moderately successful, making it clear that an accurate model should include the molecular interactions or physical mechanisms involved in transfer of load across the bone material subunits. Models of this sort cannot be constructed before more information is available about the interactions between the various organic and inorganic components. Therefore, further investigations of mechanical properties at the 'materials level', in addition to the studies at the 'structural level' are needed to fill the gap in our present knowledge and to achieve a complete understanding of the mechanical properties of bone.

Biomechanical Phenomena↗

PubMed1998

Dependence of broadband ultrasound attenuation on the elastic anisotropy of trabecular bone.

The effect of trabecular elastic anisotropy on broadband ultrasound attenuation (BUA) and bone mineral density (BMD) was investigated with human and bovine cubic cancellous bones. Ultrasonic parameters describing trabecular anisotropy were found from the three orthogonal ultrasound velocities. BMD was measured using quantitative computed tomography. Three elastic anisotropy ratios were compared to BUA in all three directions and to BMD. The combined effect of anisotropic characteristics and BMD was also correlated with BUA. The results showed that the anisotropy ratios were significantly related to BUA (p < 0.05). There was, however, no correlation between BMD and the elastic anisotropy ratios. The combination of BMD and the anisotropy produced a significantly enhanced relationship with BUA.

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PubMed1997

Elastic properties of human cortical and trabecular lamellar bone measured by nanoindentation.

An experimental investigation was undertaken to measure the intrinsic elastic properties of several of the microstructural components of human vertebral trabecular bone and tibial cortical bone by the nanoindentation method. Specimens from two thoracic vertebrae (T-12) and two tibiae were obtained from frozen, unembalmed human male cadavers aged 57 and 61 years. After drying and mounting in epoxy resin nanoindentation tests were conducted to measure Young's modulus and the hardness of individual trabeculae in the vertebrae and single osteons, and interstitial lamellae in the tibiae. Measurements on the vertebral trabeculae were made in the transverse direction, and the average Young's modulus was found to be 13.5 +/- 2.0 GPa. The tibial specimens were tested in the longitudinal direction, yielding moduli of 22.5 +/- 1.3 GPa for the osteons and 25.8 +/- 0.7 GPa for the interstitial lamellae. Analysis of variance showed that the differences in the measured moduli are statistically significant. Hardness differences among the various microstructural components were also observed.

Elasticity↗

PubMed1997

The characterization of broadband ultrasound attenuation and fractal analysis by biomechanical properties.

The purpose of this study was to show how the difference in structure affects the mechanical properties of bone and if BUA or fractal analysis is able to detect these changes in mechanical properties. A total of 38 cancellous bone cubes were obtained from seven bovine tibiae (32 specimens) and one human tibia (6 specimens). BUA was measured in the superior/inferior (SI), medial/lateral (ML), and anterior/posterior (AP) directions for each specimen. The fractal dimension was estimated by using the continuous alternating sequential filter (CASF) pyramid approach to handle fractal dimension estimation of small images. Nondestructive compressive tests were also performed in the three orthogonal directions for each sample. The correlations between BUA and density were statistically significant for all three directions. The correlation between BUA and elastic modulus varied depending on the direction in which the two parameters were measured. The best correlation was in the AP directions (r = 0.75, p < 0.0001), followed by the ML direction (r = 0.52, p = 0.0006), and finally the SI direction (r = 0.18, p = 0.28). The only significant correlation between fractal dimension and density was in the SI direction (r = 0.39, p = 0.015). There was significant correlation between fractal dimension and elastic modulus in all three directions, but the direction that exhibited the best correlation was the SI direction (r = 0.61, p < 0.0001). The correlation coefficients for the AP and ML directions were 0.45 (p = 0.0046) and 0.34 (p = 0.0377), respectively. A multivariate model, carried out to predict the elastic modulus from the BUA or fractal dimension including density, demonstrated that the correlation coefficient significantly increased in all three directions for BUA and fractal dimension. After adjustment for density, significant relationships between elastic modulus and BUA or fractal dimension were still found (p < 0.05).

Animals↗

PubMed1997

Anatomical variation of human cancellous bone mechanical properties in vitro.

The aim of the study was to assess mechanical properties of human cancellous bone in vitro. Six hundred cubic specimens of cancellous bone were obtained from the tibia, femur, patella, lumbar spine and humerus of eight subjects. The elastic properties were assessed using an ultrasonic transmission technique developed and validated by Ashman (1). The results showed that differences exist between subjects significantly (p < 0.05) and that the mechanical properties vary along the length and the periphery (about a factor 3 to 5). Cancellous bone should be considered heterogeneous and as orthotropic materials exhibiting degrees of anisotropy varying from 2 to 4. Linear and power fit elationships for cancellous bone were found approximately equal. Powers vary from 1.3 to 1.7 for axial modulus versus density and 1.3 and 2.3 for strength versus density. Finally, these results suggest the use of appropriate mechanical properties upon the type of bone for finite element analysis.

Aged↗

PubMed1996

The nonlinear transition period of broadband ultrasound attenuation as bone density varies.

The purpose of this study was to determine whether a transition period occurs between cortical and cancellous bone in the relationship between ultrasound parameters [broadband ultrasound attenuation (BUA) and ultrasonic velocity] and density. Twenty-two cancellous bone discs wee obtained from proximal bovine tibiae. Also included were three samples of human vertebral cancellous bone from an elderly female and four samples of bovine cortical bone. Ultrasonic velocity did not show any transition period as density varied from cancellous to cortical bone. Ultrasonic velocity exhibited a definite linear dependence on density over the entire range examined. However, BUA has shown a transition period as density varied. Although BUA increased linearly with density for a low density cancellous bone tested (below 0.64 g cm-3), the dependence of BUA on density is nonlinear with a downwardly inflected parabola shape when covering a wide density range (0.130-0.913 g cm-3) of cancellous bone. When one includes cortical bone, the parabola tends to level off in a slow exponential decay. This nonlinear dependence may help to understand the characteristics of BUA measurement.

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PubMed1996

An ultrasonic method for measuring the elastic properties of human tibial cortical and cancellous bone.

Ultrasonic techniques have been used to measure the elastic properties of bone. Eight human tibiae were used to determine and map the elastic properties of cortical and cancellous bone. The present study shows cortical bone to be at least orthotropic in its material symmetry. The mechanical properties of cortical bone are more homogeneous along the length than around the circumference. The variations in the properties around the quadrant of cortical bone are small, less than 10%, while differences in the properties around the circumference of cancellous bone are more apparent, approximately 5 times those of cortical bone. The elastic properties of cancellous bone exhibited inhomogeneity and some consistency pattern along both the length and the circumference.

Aged↗

PubMed1996

Broadband ultrasound attenuation value dependence on bone width in vitro.

The purpose of this study was to examine the dependence of broadband ultrasound attenuation (BUA) on bone width using 16 samples of dense bovine cancellous bone. Both BUA and density were measured simultaneously so that a dependence of BUA on bone width independent of density could be found. BUA was found to increase significantly with bone width (3.6 dB MHz-1 mm-1, r = 0.92, p < 0.0001) and this increase could not be explained by associated changes in density.

Animals↗

PubMed1995

Relations of mechanical properties to density and CT numbers in human bone.

Mechanical properties of cortical and cancellous bone from eight human subjects were determined using an ultrasonic transmission technique. Raw computerized tomography (CT) values obtained from scans of the bones in water were corrected to Hounsfield units. The correlations between CT numbers and mechanical property estimated from cortical bone were found to be low (r2 < 0.2), while these relationships for cancellous bone were found to be higher (r2 > 0.6). These results suggest that CT values may be useful in predicting mechanical properties only for cancellous bone. Poor correlations were found between modulus in the radial or circumferential direction and modulus in the superior-inferior direction for cortical bone, whereas good correlations were found between modulus in the anterior-posterior direction or medial-lateral direction and modulus in the S-I direction for cancellous bone. These results indicate that modulus in the radial or circumferential direction could not be predicted from modulus in the S-I direction for cortical bone, but could be predicted for cancellous bone. The predictive capabilities of linear and power models evaluated for cancellous bone alone were approximately equal. However, the power function gives a better fit of data at the low and high density values. The specific relationships, depending on the types of bone, that predict elastic modulus from density and CT numbers were suggested for human cortical and cancellous bone. These specific correlations may help a number of researchers develop more accurate models; however, these hypotheses should be proven by further study.

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PubMed1994

Mechanical loading thresholds for lamellar and woven bone formation.

Bone formation was measured in rat tibiae after 12 days of applied loading. Bending forces were applied using a four-point loading apparatus. Sham loads were applied at the same magnitudes as bending forces but the loading pads were arranged so that bending was minimized. Bending and sham loading were applied to the right tibiae of rats and the left tibiae served as contralateral controls. Loading was applied as a sine wave with a frequency of 2 Hz for 18 s (36 cycles) per day. The peak magnitude of applied load was 27, 33, 40, 52, and 64 N. Woven bone was observed on the periosteal surface in all animals subjected to loads of 40 N or greater. Periosteal woven bone formation occurred in both bending and sham loading groups. Woven bone formation on the periosteal surface was either absent or responded at a maximal rate if the stimulus threshold was surpassed. The amount of new woven bone and the woven bone-forming surface were independent of the magnitude of applied strain. Bone formation on the endocortical surface was exclusively lamellar. Lamellar bone formation was stimulated by applied bending of the tibia but not by sham loading. Bending strains above a loading threshold of 40 N or about 1050 mu strain increased both bone-forming surface and the mineral apposition rate and subsequently increased the bone formation rate as much as sixfold. No evidence of increased bone formation was seen for applied strains below 1050 mu strain. Examination of bulk stained sections from animals exposed to the highest applied loads showed no evidence of microcracks.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1994

A comparison of reflection and transmission ultrasonic techniques for measurement of cancellous bone elasticity.

A reflection ultrasonic technique, which offers several advantages over transmission ultrasonic techniques, has been described for elastic property measurement of bone. Ultrasonic velocities from specimens of cancellous bone were compared using a reflection ultrasound technique and the more traditional transmission ultrasonic technique. The two techniques were found to yield velocities which were reasonably well correlated (r2 = 0.74). However, a statistical difference was found between the line of identity and the regression between transmission and reflection velocities (due to an offset in the intercept). In spite of differences in intercept between velocities measured by the two techniques, significant correlation was found between the two methods, suggesting that the reflection technique can measure wave velocities meaningful to bone elasticity.

Animals↗