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Y X Qin

Publications and source records attributed to Y X Qin.

11 recordsLinked to original sources
PubMed2001

Patterns of strain in the macaque tibia during functional activity.

The strain environment of the tibial midshaft of two female macaques was evaluated through in vivo bone strain experiments using three rosette gauges around the circumference of the bones. Strains were collected for a total of 123 walking and galloping steps as well as several climbing cycles. Principal strains and the angle of the maximum (tensile) principal strain with the long axis of the bone were calculated for each gauge site. In addition, the normal strain distribution throughout the cross section was determined from the longitudinal normal strains (strains in the direction of the long axis of the bone) at each of the three gauge sites, and at the corresponding cross-sectional geometry of the bone. This strain distribution was compared with the cross-sectional properties (area moments) of the midshaft. For both animals, the predominant loading regime was found to be bending about an oblique axis running from anterolateral to posteromedial. The anterior and part of the medial cortex are in tension; the posterior and part of the lateral cortex are in compression. The axis of bending does not coincide with the maximum principal axis of the cross section, which runs mediolaterally. The bones are not especially buttressed in the plane of bending, but offer the greatest strength anteroposteriorly. The cross-sectional geometry therefore does not minimize strain or bone tissue. Peak tibial strains are slightly higher than the peak ulnar strains reported earlier for the same animals (Demes et al. [1998] Am J Phys Anthropol 106:87-100). Peak strains for both the tibia and the ulna are moderate in comparison to strains recorded during walking and galloping activities in nonprimate mammals.

Animals↗
PubMed2001

Ultrasonic wave propagation in trabecular bone predicted by the stratified model.

The objective of this study was to investigate ultrasound propagation in trabecular bone by considering the wave reflection and transmission in a multilayered medium. The use of ultrasound to identify those at risk of osteoporosis is a promising diagnostic method providing a measure of bone mineral density (BMD). A stratified model was proposed to study the effect of transmission and reflection of ultrasound wave within the trabecular architecture on the relationship between ultrasound and BMD. The results demonstrated that ultrasound velocity in trabecular bone was highly correlated with the bone apparent density (r=0.97). Moreover, a consistent pattern of the frequency dependence of ultrasound attenuation coefficient has been observed between simulation using this model and experimental measurement of trabecular bone. The normalized broadband ultrasound attenuation (nBUA) derived from the simulation results revealed that nBUA was nonlinear with respect to trabecular porosity and BMD. The curve of the relationship between nBUA and BMD was parabolic in shape, and the peak magnitude of nBUA was observed at approximately 60% of bone porosity. These results agreed with the published experimental data and demonstrated that according to the stratified model, reflection and transmission were important factors in the ultrasonic propagation through the trabecular bone.

Animals↗
PubMed2000

Encoding of location and intensity of noxious indentation into rat skin by spatial populations of cutaneous mechano-nociceptors.

The ability of a spatial population of cutaneous, Adelta, and C mechano-nociceptors to encode the location and intensity of a noxious, cutaneous indentation was examined using an isolated preparation in a rat model. Skin and its intact innervation were harvested from the medial thigh of the rat hindlimb and placed in a dish, with the corium side down, containing synthetic interstitial fluid. The margins of the skin were coupled to an apparatus that could stretch and apply compression to the skin. The skin was suspended on top of a deformable platform whose bulk, nonlinear, compressive compliance emulated that found in vivo. The isolated preparation facilitated examination of the spatial population response by eliminating the nonlinear geometry and inhomogeneous compressive compliance present in-vivo. Spatial population responses (SPR) were formed from recordings of single neurons that were stimulated by compressing the skin with an indenter (flat cylinder, 3-mm diam) at discrete intervals from the center of their receptive fields. SPR were composed of the neural responses (z axis) at each indentation location (x, y plane), and were analyzed quantitatively using nonlinear regression to fit an equation of a Gaussian surface. Both Adelta and C SPR accurately encoded the location and intensity of noxious indentation. The intensity of the stimulus was encoded in the peak neural response of the SPR, which had a nonlinear relationship to the compressive force. The location of the stimulus was encoded in the x, y position of the peak of the SPR. The position of the peak remained constant with increasing magnitudes of compressive force. The overall form of the SPR also remained constant with changes of compressive load, suggesting a possible role for encoding in the SPR some aspects of shape of a noxious stimulus.

Analysis of Variance↗
PubMed1999

Does bone perfusion/reperfusion initiate bone remodeling and the stress fracture syndrome?

Stress fractures have been proposed to arise from repetitive activity of training inducing an accumulation of microfractures in locations of peak strain. However, stress fractures most often occur long before accumulation of material damage could occur; they occur in cortical locations of low, not high, strain; and intracortical osteopenia precedes any evidence of micro-cracks. We propose that this lesion arises from a focal remodeling response to site-specific changes in bone perfusion during redundant axial loading of appendicular bones. Intramedullary pressures significantly exceeding peak arterial pressure are generated by strenuous exercise and, if the exercise is maintained, the bone tissue can suffer from ischemia caused by reduced blood flow into the medullary canal and hence to the inner two-thirds of the cortex. Site specificity is caused by the lack, in certain regions of the cortex, of compensating matrix-consolidation-driven fluid flow which brings nutrients from the periosteal surface to portions of the cortex. Upon cessation of the exercise, re-flow of fresh blood into the vasculature leads to reperfusion injury, causing an extended no-flow or reduced flow to that portion of the bone most strongly denied perfusion during the exercise. This leads to a cell-stress-initiated remodeling which ultimately weakens the bone, predisposing it to fracture.

Bone Remodeling↗
PubMed1998

Nonlinear dependence of loading intensity and cycle number in the maintenance of bone mass and morphology.

The daily stress stimulus theory of bone adaptation was formulated to describe the loading conditions necessary to maintain bone mass. This theory identifies stress/strain magnitude and loading cycle number as sufficient to define an appropriate maintenance loading signal. Here, we extend the range over which loading cycle number has been evaluated to determine whether the daily stress stimulus theory can be applied to conditions of very high numbers of loading cycles at very low strain magnitudes. The ability of a relatively high-frequency (30-Hz) and moderate-duration (60-minute) loading regimen to maintain bone mass in a turkey ulna model of disuse osteopenia was evaluated by correlating the applied strain distributions to site-specific remodeling activity. Changes in morphology were investigated following 8 weeks of disuse compared with disuse plus daily exposure to 108,000 applied loading cycles sufficient to induce peak strains of approximately 100 microstrain. A strong correlation was observed between the preservation of bone mass and longitudinal normal strain (R = 0.91) (p < 0.01). The results confirm the strong antiresorptive influence of mechanical loading and identify a threshold near 70 microstrain for a daily loading cycle regimen of approximately 100,000 strain cycles. These results are not consistent with the daily stress stimulus theory and suggest that the frequency or strain rate associated with the loading stimulus must also play a critical role in the mechanism by which bone responds to mechanical strain.

Animals↗
PubMed1998

Skeletal cell stresses and bone adaptation.

There is no tissue in which mechanical stresses have been studied in more detail than the skeletal system, this focus arising primarily because bone plays a clear structural role in the body. However, the hypothesis that the skeleton represents an optimally designed structure has contributed remarkably little to our understanding of the development and adaptive capabilities of bone tissue. Recent investigations on the consequences of mechanical, hydrostatic, and electrical stresses on the cells of bone tissue have served to redirect the discussion of bone modeling and remodeling processes. These studies have refocused attention on the importance of chronic low-level dynamic stresses in mediating the physiologic response of bone tissue. Important recent observations suggest that an approach premised on the self-organizational properties of bone tissue may lead to significant improvements in our understanding and control of bone morphologic development, adaptation, and healing.

Adaptation, Physiological↗
PubMed1996

Correlation of bony ingrowth to the distribution of stress and strain parameters surrounding a porous-coated implant.

The ability of shear strains to inhibit bony ingrowth was investigated by use of a transcortical porous-coated cylindrical plug implant in a functionally isolated turkey ulna model in which the mechanical loading environment could be accurately controlled and rigorously defined. The distribution of ingrowth at the bone-implant interface was quantified following 8 weeks of in vivo loading consisting of 100 seconds per day of a 20 Hz sinusoidal stimulus sufficient to cause a local peak strain of approximately 100 microstrain in the cortex at the bone-implant interface in four turkeys. A nonuniform but repeatable pattern of bony ingrowth, from 33 +/- 6 to 72 +/- 6% (mean +/- SE), was observed. The mechanical environment in the vicinity of the bone-implant interface was calculated using a three-dimensional elastic orthotropic finite element model. The general stress-strain state of the bone as predicted by the finite element model was validated in two additional turkeys using four three-element rosette strain gauges, while high resolution moiré interferometry was used to determine the mechanical state of the region immediately adjacent to the implant itself. Shear strains and stresses were evaluated at the interface and correlated to the pattern of bony ingrowth circumscribing the implant interface. Linear regressions between ingrowth and both shear strain and shear stress were negative, with the values of R = -0.75 and R = -0.78 (p < 0.001), respectively, indicating significant inhibition of ingrowth where shear components were maximal. These results suggest that the minimization of shear stress and strain components is a major determinant in achieving successful ingrowth of bone into a prosthesis.

Animals↗
PubMed1996

Differentiation of the bone-tissue remodeling response to axial and torsional loading in the turkey ulna.

The ability of bone tissue to differentiate between axial and torsional loading was determined with use of a functionally isolated turkey-ulna model of bone adaptation. Surface modeling and intracortical remodeling were quantified after four weeks of 5000 cycles per day of axial loading sufficient to cause 1000 microstrain normal to the long axis of the bone (five ulnae), 5000 cycles per day of torsional loading sufficient to cause 1000 microstrain of shear strain (five ulnae), or disuse (six ulnae). Of these three distinct regimens, only disuse caused a significant change in gross areal properties (12 per cent loss of bone; p < 0.05) as compared with those in the contralateral, intact control ulnae (sixteen ulnae). This finding suggested that both axial and torsional loading conditions were suitable substitutes for functional signals normally responsible for bone homeostasis. However, the intracortical response was strongly dependent on the manner in which the bone was loaded. Axial loading increased the number of intracortical pores by a factor of seven as compared with that in the controls (246 +/- 40.5 compared with 36 +/- 8.5 pores); it also increased the area lost because of porosis as compared with that in the controls (1.39 +/- 0.252 compared with 0.202 +/- 0.062 square millimeter); however, the mean size of the individual pores was similar to that in the controls (0.00565 +/- 0.0019 compared with 0.00561 +/- 0.0029 square millimeter). Conversely, torsional loading failed to increase substantially the number of pores (67 +/- 22.6 pores), the area of bone lost because of porosis (0.352 +/- 0.114 square millimeter), or the size of the pores (0.00525 +/- 0.0035 square millimeter) as compared with those in the controls. Although disuse failed to increase substantially the number of intracortical pores (59 +/- 22.4 pores), significant area (1.05 +/- 0.35 square millimeters; p < 0.05) was lost within the cortex because of a threefold increase in the mean size of each pore (0.0178 +/- 0.0126 square millimeter). It appears that bone tissue can readily differentiate between distinct components of the strain environment, with strain per se necessary to retain coupled formation and resorption, shear strain achieving this goal by maintaining the status quo, and axial strain increasing intracortical turnover but retaining coupling. While it is clear that load influences bone mass and morphology, it is also clear that specific parameters within the strain environment have distinct strategic roles in defining this architecture.

Adaptation, Physiological↗
PubMed1989

Selection of a Brucella vaccine strain of low residual virulence by chemical mutagenesis.

Following incubation of the oral vaccine Brucella suis strain 2 with diethyl sulphate (DES), a mutant designated strain S105 was selected by screening surviving bacteria for reduced virulence for mice. Strain 105 also showed low residual virulence for guinea-pigs and, unlike the parent strain, did not initiate abortion in pregnant sheep and goats after parenteral administration. Nevertheless, it was as effective as the parent strain in stimulating protective immunity to Brucella melitensis when given as an oral vaccine to sheep under both experimental and field conditions.

Animals↗
PubMedDate not supplied

Whole-body vibration in the skeleton: development of a resonance-based testing device.

Whole-body vibration (WBV) has been demonstrated to have a strong influence on physiological systems, ranging from severely destructive to potentially beneficial. Unfortunately, the study of WBV in a controlled manner is commonly constrained by space and budgetary factors, particularly where vibration in the low frequency range is considered. In the work presented here, a small, low-cost device for performing WBV of the human skeleton is developed to assist in studies of vertical acceleration in a clinical setting. The device design consists of a spring-supported plate driven by an 18 N peak-force electromagnetic actuator, and the associated driving and monitoring electronics. Animal and human lumped-mass models have been coupled with a model of the loading device to seek a resonance response in the vicinity of 30 Hz. This approach minimizes the loading requirements of such a device, and thus a major component of the cost, yet can provide peak accelerations of 0.15 g at a frequency of 30 Hz in a small, lightweight package capable of use in a clinical or laboratory setting.

Acceleration↗