Bone abnormalities in adolescent leptin-deficient mice

Ob/ob and db/db mice have different aberrations in leptin signaling that both lead to abnormalities in bone mineral density (BMD), and bone histological and histomorphometric outcomes. A few studies have directly compared bone metabolism in ob/ob and db/db mice, and biomechanical strength properties that are surrogate measures of fracture risk, have not been extensively studied. This study compared bone mineral content (BMC), BMD and biomechanical strength properties of femurs and lumbar vertebrae among 10 week old male ob/ob, db/db and C57Bl/6 wildtype (WT) mice. Femurs and lumbar vertebrae were specifically studied to determine if trabecular and cortical bone are regulated by leptin in a similar manner in ob/ob and db/db mice. Femurs of ob/ob and db/db mice had lower BMC, BMD and biomechanical strength properties, including peak load, compared to WT mice. In contrast, lumbar vertebrae BMC and BMD did not differ among genotypes, nor did the peak load from compression testing of an individual lumbar vertebra differ among groups. These findings suggest that leptin deficiency in adolescent male mice first results in changes in femurs, a representative long bone, and alterations in lumbar vertebrae may occur later in life.     

The long-term effect of ovariectomy on the quality and quantity of cancellous bone in young macaques

The effect of ovariectomy on the quality and quantity of cancellous bone using the young cynomolgus monkey was evaluated after a 2-year period. The bodies of the second lumbar vertebrae were analyzed for changes in bone mineral quality using density fractionation, chemical analysis, and X-ray diffraction techniques. Changes in bone tissue quality and quantity were evaluated using bone histomorphometry and image analysis. The experimental group (n=14) was made surgically menopausal (bilaterally ovariectomized), compared with intact controls (n=16), and then sacrificed after a 2-year period. There was a non-significant shift in the mineralization profile towards less dense bone in the ovariectomized (OVX) vertebrae compared with controls. Physical characteristics of the bone mineral in terms of crystal size or strain were unaffected by OVX. There was a parallel increase in mineral content with fractions of increasing density, however there was no difference in mineral content or the Ca/P ratio in each fraction between treatment groups. Histomorphometric analysis for structural parameters demonstrated no difference in bone volume between control and OVX groups. There was no significant change in trabecular width in the OVX vertebrae compared with controls. There was a significant increase in both osteoid volume and osteoid surface in the OVX vertebrae (P<0.001). Trabecular architecture as measured by image analysis was unchanged. There was a significant increase in eroded surface in the OVX vertebrae (P<0.03) compared with the controls. In conclusion, young, ovariectomized female cynomolgus macaques do not appear to be a useful animal model for the study of postmenopausal bone loss, however they may be a useful model to evaluate skeletal pathology which might be observed after surgical ovariectomy in young human females.     

Accuracy and precision of dual-energy X-ray absorptiometry for body composition measurements in rhesus monkeys

Accuracy of body composition measurements by dual-energy X-ray absorptiometry (DXA) was compared with direct chemical analysis in 10 adult rhesus monkeys. DXA was highly correlated (r-values > 0.95) with direct analyses of body fat mass (FM), lean mass (LM) and lumbar spine bone mineral content (BMC). DXA measurements of total body BMC were not as strongly correlated (r-value = 0.58) with total carcass ash content. DXA measurements of body FM, LM and lumbar spine BMC were not different from data obtained by direct analyses (P-values > 0.30). In contrast, DXA determinations of total BMC (TBMC) averaged 15%, less than total carcass ash measurements (P = 0.002). In conclusion, this study confirms the accurate measurement of fat and lean tissue mass by DXA in rhesus monkeys. DXA also accurately measured lumbar spine BMC but underestimated total body BMC as compared with carcass ash determinations.     

Adiponectin is a negative regulator of bone mineral and bone strength in growing mice

Obesity is associated with increased bone mineral density (BMD) but the mechanism for this is unclear. Serum levels of the adipokine adiponectin are inversely correlated with obesity, but results from studies on its relationship to bone mass are conflicting. The objective of this study was to compare bone mineral content (BMC), BMD and biomechanical strength properties of femur and lumbar vertebrae in 8- and 16-week old adiponectin transgenic mice (AdTg). These mice exhibit significantly elevated circulating adiponectin but have similar body weights compared to wild-type (WT) littermates that were used as controls. Female AdTg mice displayed significantly lower femur BMC at 8 and 16 weeks of age and femur neck peak load was significantly lower in 8-week old AdTg mice of both genders compared to controls. The peak load from compression testing of an individual lumbar vertebra was significantly lower in female AdTg mice compared to WT at 8 weeks, and this difference persisted at 16 weeks of age. In addition, lumbar vertebrae BMC was significantly lower in 16-week old male AdTg mice compared to WT although vertebra peak load was not different. Serum adiponectin levels were inversely correlated with femur BMC. In summary, elevated circulating adiponectin inhibits the acquisition of bone mass in growing mice and results in decreased biomechanical measures of functional strength that are surrogate measures of susceptibility to fractures. These results support a role for circulating adiponectin as a metabolic link that can explain, at least in part, the positive relationship between obesity and both bone mass and reduced susceptibility to fractures.     

Bone measurement by enhanced contrast image analysis: ovariectomized and intact Macaca fascicularis as a model for human postmenopausal osteoporosis

This paper presents an image enhancement and analysis system (DARWIN) based on an inexpensive microcomputer and applies the system to two bone morphometry problems relevant to postmenopausal osteoporosis. Using ovariectomized and intact female Macaca fascicularis as a model, we examined the radiodensity of the sixth lumbar vertebra and the cross-section area of the right femur. Significantly lower bone density was observed in the vertebral segments of the ovariectomized animals. No significant differences were observed in comparisons of the femoral cross sections. The reduction in radiographic density of the ovariectomized animals' vertebrae is similar to that observed in postmenopausal women, supporting the use of female cynomolgus macaques as models of bone loss in postmenopausal osteoporosis.     

Flaxseed oil and inflammation-associated bone abnormalities in interleukin-10 knockout mice

Interleukin-10-/- (IL-10) knockout (KO) mice develop an intestinal inflammation that closely mimics human inflammatory bowel disease (IBD) which is accompanied by inflammation-associated bone abnormalities and elevated serum proinflammatory cytokines. The objective of this study was to use the IL-10 KO mouse model to determine whether flaxseed oil (FO) diet, rich in alpha-linolenic acid (ALA), attenuates intestinal inflammation and inflammation-associated bone abnormalities, compared to a corn oil (CO) control diet. Male wild-type (WT) or IL-10 KO mice were fed a 10% CO or 10% FO diet from weaning (postnatal day 28) for 9 weeks. At necropsy, serum, intestine, femurs and lumbar vertebrae were collected and analyzed. IL-10 KO mice fed CO had lower femur bone mineral content (BMC; P<.001), bone mineral density (BMD; P<.001), peak load (P=.033) and lumbar vertebrae BMD (P=.02) compared to WT mice fed either diet. Flaxseed oil had a modest, favorable effect on IL-10 KO mice as femur BMC, BMD and peak load were similar to WT mice fed CO or FO. In addition, lumbar vertebra BMD was similar among IL-10 KO mice fed FO and WT mice fed CO or FO. The fact that FO attenuated serum tumor necrosis factor-alpha (TNF-alpha) among IL-10 KO mice suggests that the positive effects of FO on femur BMC, BMD, peak load and vertebral BMD in IL-10 KO mice may have been partly mediated by changes in serum TNF-alpha. In conclusion, these findings suggest that a dietary level of ALA attainable from a 10% flaxseed oil diet results in modest improvements in some bone outcomes but does not attenuate intestinal inflammation that is characteristic of IL-10 KO mice.     

Iron restriction negatively affects bone in female rats and mineralization of hFOB osteoblast cells

We previously reported that severe iron deficiency negatively affects bone microarchitecture. Here we determined whether marginal iron restriction that reflects some human consumption patterns could have similar consequences. Thirty-two weanling female rats were randomly divided into four groups and fed the following diets for 10 weeks: (i) iron-adequate, calcium-adequate (FeA:CaA), (ii) calcium-restricted (FeA:CaR), (iii) iron-restricted (FeR:CaA), and (iv) both calcium- and iron-restricted (FeR:CaR) diets. DEXA analysis revealed that CaR decreased bone mineral density (BMD), and FeR decreased whole-body bone mineral content (BMC). Iron-restricted and calcium-restricted groups had lower BMD than did their adequate counterparts. All treatment-restricted groups had lower BMD in the fourth lumbar (L-4) vertebrae than the FeA:CaA group. Vertebrae BMD was lower in all treatment groups compared to the control group, and for BMC, the CaR groups were lower than the CaA groups and the FeR groups were lower that the FeA groups, and BMC were lower in iron- and calcium-restricted groups. The microarchitecture of the L-4 vertebrae was compromised in FeA:CaR, FeR:CaA, and FeR:CaR: (i) the connectivity density was reduced by FeR and by CaR; and (ii) trabecular number was decreased and trabecular separation was increased by FeR. Cortical thickness of the femur was reduced by both FeR and CaR. Finite element analysis revealed that L-4 vertebrae from the FeR:CaA group had greater internal stress with an applied force than the FeA:CaA group and, thus, would be more likely to break. Chelation of iron in cultured osteoblast cells impaired mineralization but had no impact upon Type I collagen deposition. Iron depletion, similar to that occurring among some human populations, reduced bone strength and microarchitecture based on the in vivo and in vitro results reported here. Impaired mineralization with iron depletion appears to be a possible mechanism for the observed bone abnormalities.     

Calcium metabolism in premenopausal women treated by a Gn-RH agonist for uterine myoma

Eleven premenopausal women with uterine myoma who received 300 micrograms of intranasal Gn-RH agonist (buserelin) three times daily for 6 months participated in this study. Serum estradiol, some parameters related to calcium metabolism and bone mineral density of the lumbar vertebrae assessed by quantitative computerized tomography were evaluated prior to, at the end of and 3 months after the treatment. Hypo-estrogenism was sustained during the treatment period. Calcitonin levels decreased rapidly after the first 2 weeks of the treatment and the fasting urinary hydroxyproline to creatinine excretion value increased in 1 month. Both serum alkaline phosphatase and osteocalcin increased slightly during the treatment. The serum m-parathyroid hormone levels showed no significant changes. There was no significant reduction in the mean lumbar vertebral bone mineral content (BMC) at the end of the treatment, but 4 out of 11 cases showed a decrease in BMC, which returned to the pretreatment level in 3 months after the cessation of treatment. From these findings, this therapy appears to have some effects on calcium metabolism during medication, but no adverse ones in the 3 months after treatment.     

Bronchoconstriction in nonhuman primates: a species comparison

Bronchoconstriction is a characteristic symptom of various chronic obstructive respiratory diseases such as chronic obstructive pulmonary disease and asthma. Precision-cut lung slices (PCLS) are a suitable ex vivo model to study physiological mechanisms of bronchoconstriction in different species. In the present study, we established an ex vivo model of bronchoconstriction in nonhuman primates (NHPs). PCLS prepared from common marmosets, cynomolgus macaques, rhesus macaques, and anubis baboons were stimulated with increasing concentrations of representative bronchoconstrictors: methacholine, histamine, serotonin, leukotriene D? (LTD?), U46619, and endothelin-1. Alterations in the airway caliber were measured and compared with previously published data from rodents, guinea pigs, and humans. Methacholine induced maximal airway constriction, varying between 74 and 88% in all NHP species, whereas serotonin was ineffective. Histamine induced maximal bronchoconstriction of 77 to 90% in rhesus macaques, cynomolgus macaques, and baboons and a lesser constriction of 53% in marmosets. LTD? was ineffective in marmosets and rhesus macaques but induced a maximum constriction of 44 to 49% in cynomolgus macaques and baboons. U46619 and endothelin-1 caused airway constriction in all NHP species, with maximum constrictions of 65 to 91% and 70 to 81%, respectively. In conclusion, PCLS from NHPs represent a valuable ex vivo model for studying bronchoconstriction. All NHPs respond to mediators relevant to human airway disorders such as methacholine, histamine, U46619, and endothelin-1 and are insensitive to the rodent mast cell product serotonin. Only PCLS from cynomolgus macaques and baboons, however, responded also to leukotrienes, suggesting that among all compared species, these two NHPs resemble the human airway mechanisms best.     

Standardized data and relationship between bone growth and bone metabolism in female G?ttingen minipigs.

Minipigs have been studied as a model of osteoporosis. However, little information is available regarding their bone physiology. We established standardized bone data and investigated the relationship between bone growth and bone metabolism in female minipigs. Blood and urine samples were obtained from 53 female G?ttingen minipigs, 3-76 months of age, for measurement of bone biomarkers (i.e., BAP, OC, NTX, and DPD). The lumbar vertebra and femur were excised to determine the growth plate condition, bone length, bone mineral content (BMC), and bone mineral density (BMD). High levels of bone biomarkers were observed during the initial period after birth, decreasing thereafter with age. Bone biomarkers were confirmed to be highly correlated with age (R(2) > 0.7). The growth plates of the lumbar vertebra and the femur began to close at 21 and 25 months of age, respectively, and closed completely at 42 months of age. Bone length increased rapidly before growth plate closure, and reached a peak at 21 and 28 months of age in the lumbar vertebra and the femur, respectively. The levels of BMC and BMD increased rapidly before growth plate closure, and continued to increase slowly until 76 months of age. A high negative correlation (-0.855 < r < -0.711, p<0.001) was confirmed between the bone biomarkers and the bone measurement data. These results indicate that the bone turnover velocity is consistent with the bone growth velocity in female G?ttingen minipigs.     

Relationships between anthropometric, body composition and bone mineral parameters in 7-8-year-old rhythmic gymnasts compared with controls

The aim of the study was to investigate the relationships between specific anthropometric (9 skinfolds, 13 girths, 8 lengths and 8 breadths), body composition (body fat %, fat free mass [FFM], fat mass [FM]) parameters and bone mineral parameters (bone mineral density [BMD], bone mineral content [BMC) in young rhythmic gymnasts and same age controls. Eighty nine 7-8-year-old girls participated in this study and were divided to the rhythmic gymnast's (n = 46) and control (n = 43) groups. Body composition was determined by dual energy X-ray absorptiometry (FFM, FM, body fat %, BMD and BMC). Body fat % and FM were lower and BMD and BMC values at lumbar spine (L2-L4) and femoral neck were higher in rhythmic gymnasts compared with controls. All measured skinfold thicknesses were thicker in controls. In girths, lengths and widths there were only few significant differences between the groups. Stepwise multiple regression analysis indicated that skinfold thicknesses (supraspinale and medial calf) influenced L2-L4 BMD only in controls 38.2% (R2x100). Supraspinale and iliac crest skinfold thicknesses characterised L2-L4 BMC 43.9% (R2x100). Calf girths influenced BMD in L2-L4 52.3% (R2x100) in controls. BMC in L2-L4 was dependent only on mid-thigh girths 35.9% (R2x100). BMD in L2-L4 was dependent on tibiale-laterale height 30.0% (R2x100). Biiliocristal breadths together with sitting height characterised BMC in L2-L4 BMD 62.3% (R2x100). In conclusion, we found that the relationships between anthropometry, body composition and bone parameters in young rhythmic gymnasts are weak. In control group first of all lower body anthropometric parameters significantly correlated with BMD and BMC in spine.     

Effect of in utero exposure to diethylstilbestrol on lumbar and femoral bone, articular cartilage, and the intervertebral disc in male and female adult mice progeny with and without swimming exercise

Introduction

Developmental exposure to estrogens has been shown to affect the musculoskeletal system. Furthermore, recent studies have shown that environmental exposure to estrogen-like compounds is much higher than originally anticipated. The aim of this study was to determine the effects of diethylstilbestrol (DES), a well-known estrogen agonist, on articular cartilage, intervertebral disc (IVD), and bone phenotype.

Methods

C57Bl/6 pregnant mice were dosed orally with vehicle (peanut oil) or 0.1, 1.0, and 10 μg/kg/day of DES on gestational days 11 to 14. Male and female pups were allowed to mature without further treatment until 3 months of age, when swim and sedentary groups were formed. After euthanasia, bone mineral density (BMD), bone mineral content (BMC), bone area (BA), and trabecular bone area (TBA) of the lumbar vertebrae and femur were measured by using a PIXImus Bone Densitometer System. Intervertebral disc proteoglycan was measured with the DMMB assay. Histologic analysis of proteoglycan for IVD and articular cartilage was performed with safranin O staining, and degeneration parameters were scored.

Results

The lumbar BMC was significantly increased in female swimmers at both the highest and lowest dose of DES, whereas the femoral BMC was increased only at the highest. The males, conversely, showed a decreased BMC at the highest dose of DES for both lumbar and femoral bone. The female swim group had an increased BA at the highest dose of DES, whereas the male counterpart showed a decreased BA for femoral bone. The TBA showed a similar pattern. Proteoglycan analysis of lumbar IVDs showed a decrease at the lowest doses but a significant increase at the highest doses for both males and females. Histologic examination showed morphologic changes of the IVD and articular cartilage for all doses of DES.

Conclusions

DES significantly affected the musculoskeletal system of adult mice. Results suggest that environmental estrogen contaminants can have a detrimental effect on the developmental lumbar bone growth and mineralization in mice. Further studies measuring the impact of environmental estrogen mimics, such as bisphenol A, are then warranted.     

Different skeletal regional response to continuous brain infusion of leptin in the rat

This study was designed to evaluate whether or not continuous intracerebroventricular infusion of leptin (1.5 microg/rat/24 h, for 28 days) produced different regional response on the skeleton of growing rats. Leptin reduce the accretion of total femoral bone mineral content (BMC) and density (BMD). This effect was related to a reduction of metaphyseal femur as no changes were detected in the diaphysis. Despite the reduced accretion in the volumetric of both femur and tibia compared to controls, leptin had no significant effects on the lumbar vertebrae. Urine deoxypyrydinoline and serum osteocalcin remained more elevated in the leptin-treated group as compared to controls. The results demonstrate that long-term central infusion of leptin activates bone remodeling with a negative balance. Leptin induces distinct responses in the different structure of bone and in the axial and appendicular skeleton.     

In vivo whole body and appendicular bone mineral density in rats: a dual energy X-ray absorptiometry study

Bone mineral density (BMD) of the whole body and hind limb of young adult rats, with and without a sham-operated stifle joint was studied, using dual energy x-ray absorptiometry (DEXA) at three time points. Data from the whole body scan were used for analyses of BMD, bone mineral content (BMC), fat, lean, body weight (BW), percentage of BMC (%BMC), percentage of fat (%fat), and percentage of lean (%lean), none of which were significantly different between the groups at any time point. Significant (P < 0.05) differences in BMD, BMC, %BMC, BW, fat, %fat, and %lean were apparent at the second and third scans, compared with the initial scan, within both groups. Changes in whole body BMD, BMC, and %BMC as well as BW were highly correlated with time in both groups. In the hind limb scans, regions of interest (ROIs) were created to obtain values of BMD and BMC from the whole femur, whole tibia including the fibula, distal portion of the femur, and proximal portion of the tibia. Significant differences were not found between the groups for any ROIs. However, significant BMD and BMC increases were evident in all ROIs at the second and third scans, compared with the initial scan. Similar to those in the whole body scan, BMD and BMC obtained from ROIs were highly correlated with time. The positioning technique for the whole body and appendicular scans was analyzed by calculating percentage of the coefficient of variation (%CV) at the beginning of the study. The %CV was low and acceptable in ROIs for the hind limb and for all parameters of the whole body scan, except fat. The results suggest that in vivo DEXA scanning of the rat whole body and appendicular skeleton is highly reproducible and useful to study the whole skeleton, as well as a region of a long bone of the rat. Values for the sham-operated rats were not significantly different from those for the untreated controls, which suggests that soft tissue damage around the stifle joint did not alter BMD in the subchondral bone of the distal portion of the femur and proximal portion of the tibia.     

Fundectomy-evoked osteopenia in pigs is mediated by the gastric-hypothalamic-pituitary axis

The aim of the study was to determine the effects of gastric impairment in pigs on the axial and peripheral skeletal system properties and to test the hypothesis that fundectomy-evoked osteopenia is related to disturbed gastric-hypothalamic-pituitary axis function. Forty-day-old male piglets were subjected to experimental fundectomy (FX group, n = 6) to induce osteopenia, while sham operation was performed in the controls (SHO group, n = 6). At the age of 8 months, serum samples were collected, and the animals were sacrificed to obtain lumbar vertebrae (L1-L6) and right humerus for analysis. Using quantitative computed tomography (QCT) and dual-energy x-ray absorptiometry (DEXA) methods, bone mineral density and bone mineral content of the vertebrae and humerus were measured. The compression and three-point bending tests were applied to determine mechanical properties of lumbar vertebrae and humerus, respectively. Furthermore, geometric properties of humerus were assessed. Serum concentrations of ghrelin, growth hormone (GH), insulin-like growth factor-1 (IGF-1), and selected macro- and microelements were also determined. Performed fundectomy decreased body weight in pigs by 66% compared with pair-fed sham operated pigs (P < 0.0001). Bone weight, bone mineral density, and bone mineral content of the lumbar vertebrae and humerus were significantly decreased in the fundectomized pigs (P < 0.01). Mechanical parameters of the lumbar spine and humerus were decreased after the fundectomy, as well. Serum concentrations of ghrelin, GH, and IGF-1 were lowered by 74.4%, 90.6%, and 54.6% in the fundectomized pigs, respectively (all P < 0.001). Moreover, the serum concentrations of calcium, magnesium, iron and copper in the fundectomized animals were significantly decreased by 15.5%, 45.3%, 26.7%, and 26.2%, respectively (P 相似文献   

Differences in vertebral structure and strength of inbred female mouse strains

This study assessed mouse strain-related differences in vertebral biomechanics and histomorphometry in inbred mice strains shown to differ in bone mineral content (BMC) and areal density (BMD) (as measured by pDEXA). Lumbar vertebrae L3 to L5 were collected from three mice strains (C3H/HeJ[C3], C57BL/6J[B6], and DBA/2J[D2], n=12/strain, 4-month-old female, 22.2 +/- 0.3g). BMC and BMD were measured in L3 and L4 using peripheral dual energy x-ray absorptiometry. The L4 vertebral body was then mechanically tested in compression to determine structural properties (ultimate/yield load, stiffness) from load-displacement curves and derive apparent material properties (ultimate/yield stress, and modulus of elasticity). L5 was processed for histomorphometric evaluation. Vertebral BMC and BMD were greater in C3 than in B6 and D2 mice. Vertebral trabecular/cancellous bone volume was smaller in C3 than in D2 and B6 mice. Trabecular bone formation rates were greater in D2 than in B6 and C3 mice. Osteoid surface was smaller in C3 mice than in B6 and D2 mice. Differences in osteoclast and mineralizing surfaces were not detected among the three mouse strains. In addition, there were no significant differences in biomechanical properties between the three strains. Despite the greatest BMC and areal BMD in C3 mice, the lack of strain-related differences in vertebral body strength data suggests that the biomechanical properties may be affected by the bone distribution and/or complex combination of cortical and cancellous bone at this site.     

Effect of parity on bone mineral density in female rhesus macaques from Cayo Santiago

This cross-sectional study investigates the relationship between parity, bone mineral density, and spontaneous osteopenia/osteoporosis in a large skeletal population of female rhesus macaques (Macaca mulatta) from the free-ranging colony of Cayo Santiago, Puerto Rico. The sample consists of 119 mature female monkeys aged 4.0-22.2 years at time of death. The data consist of measurements of bone mineral content (BMC) and bone mineral density (BMD), obtained from dual-energy X-ray absorptiometry (DEXA) of the last lumbar vertebra. After controlling for age, there is a significant increase in BMD of the spine with increasing parity (P = 0.0006), up to a parity of 7 offspring. Thus, high parity initially has a positive effect on BMD in female rhesus monkeys, but this positive effect disappears with parities that are greater than 7 offspring. After controlling for parity, however, age has a negative (P = 0.015) effect on BMD, beginning several years after the attainment of peak BMD (age 9.5 years). Thus, it appears that parity initially mitigates the effects of aging, but the positive effect of parity on BMD is eventually overwhelmed by the aging process. Mean BMC and BMD values are higher in parous females compared to nulliparous females in the same age range. Similarly, females with low parity have significantly lower mean BMD values than do age-matched high-parity controls, and the frequency of osteopenia and osteoporosis is greater in low-parity females. Forty-three percent (43%) of the osteopenic/osteoporotic females in the sample are members of the low-parity group, even though it composes only 13% (16/119) of the entire sample. This study demonstrates that the free-ranging female rhesus monkeys from Cayo Santiago are a good nonhuman primate model for the study of bone mineral density, parity, osteopenia, and osteoporosis.     

Hydraulic resistance and permeability in human lumbar vertebral bodies

Hydraulic resistance (HR) was measured for ten intact human lumbar vertebrae to further understand the mechanisms of fluid flow through porous bone. Oil was forced through the vertebral bodies under various volumetric flow rates and the resultant pressure was measured The pressure-flow relationship for each specimen was linear. Therefore, HR was constant with a mean of 2.22 +/- 1.45 kPa*sec/ml. The mean permeability of the intact vertebral bodies was 4.90x10(-10) +/- 4.45x10(-10) m2. These results indicate that this methodology is valid for whole bone samples and enables the exploration of the effects of HR on the creation of high-speed fractures.     

Preparation and characterization of new challenge stocks of SIVmac32H J5 following rapid serial passage of virus in vivo

BACKGROUND: A new challenge stock of the simian immunodeficiency virus SIVmacJ5 has been produced following passage in vivo. METHODS: SIVmacJ5 3/92 (J5M), was passaged serially through cynomolgus macaques (Macaca fascicularis) by intravenous inoculation of infected spleen cells isolated and prepared 14 days post-infection. Two challenge stocks, SIVmacJ5 S61MLN and SIVmacJ5 S62spl, were prepared by culture of lymphoid tissue ex vivo. RESULTS: These virus stocks appeared better adapted for replication in M. fascicularis as demonstrated by a greater persistence of recoverable live virus from the periphery and increased pathology in lymphoid tissues 20 weeks post-challenge as detected by immunohistochemistry. Sequence analysis of the envelope gene from these stocks did not identify marked diversification of sequence as a result of this procedure. CONCLUSIONS: These stocks display more robust peripheral persistence and tissue pathology in cynomolgus macaques and should prove valuable analysing recombinant vaccines based upon SIVmacJ5 transgenes.