Age-related changes in the compressive strength of cancellous bone. The relative importance of changes in density and trabecular architecture

Ectopic atrial tachycardia (EAT) is a rare but reversible cause of dilated cardiomyopathy (DCMP). The diagnosis and the definite control of the arrhythmia are essential for the regression of DCMP. Unfortunately, conventional antiarrhythmic drugs usually fail to control the arrhythmia, and the results of surgery or direct current ablation are suboptimal. Recently, radiofrequency (RF) catheter ablation has been evolving as a safe and effective therapy for EAT. This report describes the RF ablation treatment of a 14-year-old boy with DCMP secondary to chronic EAT. Activation mapping was used for the purpose of identifying the focus origin located just anterior to the coronary sinus os. RF energy applied at this focus successfully terminated the tachycardia. No complications related to the procedure were observed. RF ablation not only caused elimination of the EAT but also led to improvement in left ventricular function as early as two weeks after the procedure, and complete resolution of DCMP in three months.     

Prediction of vertebral and femoral strength in vitro by bone mineral density measured at different skeletal sites

The aim of the present study was to investigate the prediction of vertebral and femoral strength in vitro by bone mineral density (BMD) measured at different skeletal sites. The third lumbar vertebral body, the right proximal femur, and the right calcaneus were removed from 38 male and 32 female cadavers (mean age 69 years, range 23-92 years). Areal BMD of all bone specimens was determined by dual-energy X-ray absorptiometry (DXA). The failure load of the vertebral body and the femur was determined by mechanical testing. Vertebral and femoral strength were both greater in males than females (p < 0.01), as was BMD at all sites (p < 0.01). Vertebral strength correlated well with vertebral BMD (r2 = 0.64) but was only moderately correlated with BMD measured at the femur (r2 = 0.36) or the calcaneus (r2 = 0.18). Femoral strength showed the highest correlations with femoral BMD (r2 = 0.88) and somewhat weaker relationships with BMD at the vertebra (r2 = 0.50) and the calcaneus (r2 = 0.54). BMD values at the vertebra, femur, and calcaneus were only moderately interrelated (r2 = 0.31-0.65), and vertebral strength correlated only modestly with the strength of the femur (r2 = 0.36). These in vitro results support the concept that optimal prediction of vertebral or femoral strength by DXA requires site-specific assessments.     

Dual-energy x-ray absorptiometry of raloxifene effects on the lumbar vertebrae and femora of ovariectomized rats

A new potential therapeutic agent for postmenopausal osteoporosis, raloxifene, previously known as keoxifene, was evaluated by x-ray densitometry and more traditional techniques in quantitating the short-term (4-5 weeks) effects of ovariectomy on bones from 6-month-old rats. A Hologic QDR 1000/W and, to a limited extent, a Lunar DPXL, was used to quantitate ovariectomy, estrogen replacement, and raloxifene effects on vertebrae, femora, and tibiae. Both instruments performed well with precisions of 1.6% (Hologic) and 0.9% (Lunar) for anesthetized rats, which improved to 0.4% (Hologic) and 0.5% (Lunar) when the same rats were frozen. The lumbar vertebrae L1-4 showed a 12% decrease in bone mineral density 4 weeks after ovariectomy, compared with a 9% decrease for femora. Tibiae were also examined, but edge-detection problems prevented reproducible analysis of this site in vivo. The decrease in bone mineral density postovariectomy, especially for femora, was found to include both an increase in the projected area and a slight but not significant decrease in the bone mineral content of L1-4 and femora. These changes in density parameters of femora were supported by a decrease in dry weight and volume and a marginal increase in the second moment of inertia I for the identical femora examined ex vivo. Examination of individual lumbar vertebrae L1-5 suggested that the bone mineral density of L3 changes most dramatically in response to ovariectomy, but present techniques lack the spatial resolution and precision to quantitate bone changes reliably in individual vertebrae. 17 beta-Estradiol administered at 100 micrograms/kg/day subcutaneously inhibited ovariectomy effects on L1-4 bone mineral density, femoral moment of inertia, dry weight, and volume and to a lesser extent, femoral bone mineral density. A nonsteroidal compound, raloxifene HCl, at 1 mg/kg/day per os, had bone effects and effects on body weight that were largely indistinguishable from those of 17 beta-estradiol; however, raloxifene did not produce the uterotrophic effects observed with estrogen. The half-maximal efficacious dose of raloxifene on L1-4 bone mineral density was between 0.1 and 1.0 mg/kg/day per os. These data show that dual-energy x-ray absorptiometry compares favorably with traditional methods in quantitating bone changes caused by ovariectomy in small rodents, that L1-4 is a more sensitive region than whole femora in evaluating the effect of estrogen deficiency on bone loss, and the raloxifene may have promise as a treatment for conditions characterized by excessive bone loss after ovariectomy.     

混凝土试件抗压强度数据的可靠性分析

每组混凝土的抗压强度代表值由3个立方体试件的抗压强度的算术平均值确定,现行标准中只考虑了这个代表值,而没有全面深入分析这3个数据所隐含的其它信息,文章试图从数理统计角度分析这些隐含信息,并分析如何使用这些信息对混凝土试件抽样和对测试人员的工作质量进行控制。     

The effects of risedronate on canine cancellous bone remodeling: three-dimensional kinetic reconstruction of the remodeling site

To investigate the dose-dependent effects of risedronate on cancellous bone remodeling, adult female beagle dogs were treated with either placebo, 0.1, 0.5, or 2.5 mg/kg/day of risedronate orally in an intermittent cyclic regimen (7 days on 21 days off), repeated three times. Iliac cancellous bone samples were subjected to histomorphometric analysis and three-dimensional (3-D) kinetic reconstruction of the remodeling site was performed. In the 0.1 mg/kg dose group, resorption and activation indices were no different from the placebo group. However, wall thickness was increased resulting in a positive bone balance at the level of the remodeling unit. In the 0.5 and 2.5 mg/kg dose groups, a dose-dependent reduction in activation frequency and tissue level bone formation was observed. Resorption rates were also significantly decreased, 60% and 80% for the 0.5- and 2.5-mg/kg groups, respectively. An approximate 25% reduction in final erosion depth was noted in both these groups. Analyses of the growth curves of the bone packet confirmed that the kinetics of the growth of a completed packet were different in the 0.5- and 2.5-mg/kg dose groups compared with placebo. These changes were associated with a significant increase in the final wall thickness in both groups indicating no net impairment of osteoblast function. These increases in wall thickness in combination with the reductions in final erosion depth in the 0.5 and 2.5 mg/kg groups resulted in a significant dose-dependent positive bone balance. This pharmacological profile suggests that risedronate may be of therapeutic utility in the treatment of metabolic bone diseases where reductions in activation frequency and resorptive cell activity at the level of the remodeling unit are a therapeutic goal.     

含水率对砖砌体抗压强度影响的试验研究

由于洪水浸泡,砌体结构的承载能力将会受到影响,甚至出现倒塌.为了掌握不同含水率对砖砌体结构强度的影响规律,确定浸泡后结构的承载能力,有必要对含水率影响砖砌体抗压强度进行研究.通过对不同浸泡时间的砖砌体试件的抗压强度进行测试,对比了不浸泡、浸泡2 d、7 d、14d砖砌体试件的抗压强度,得到了砖砌体试件抗压强度随浸泡时间的变化规律.     

Connectivity and the elastic properties of cancellous bone

The effect of ibuprofen enantiomers on the stereoselective binding of 3-acyloxy-1,4-benzodiazepines to human serum albumin (HSA) was studied using both native and Sepharose-immobilized protein. (S)-Lorazepam acetate exhibited considerably enhanced binding, especially in the presence of (+)-(S)-ibuprofen. The phenomenon is an indication of cooperative allosteric interaction between different binding sites during multiple cobinding of two ligands.     

The effect of fiber-matrix debond energy on the matrix cracking strength and the debond shear strength

The matrix cracking model given by Budiansky, Hutchinson and Evans [J. Mech. Phys. Solids34, 167 (1986)] is extended to include the effect of fiber-matrix bonding in a unidirectional fiber-reinforced composite. By use of an energy balance analysis, the work of debonding Γ_d is related to a characteristic critical interface shear stress τ_d and to the frictional interface sliding resistance τ_f by the expression τ_d − τ_f = √4G_mΓ_d/av, where G_m is the matrix shear modulus, a, the fiber radius, and v the function of fiber volume exceeds the background fiber tensile stress far from the crack by a fixed calculable amount. Finally, the combined effect of τ_f and adhesion on the intercrack spacing is predicted for the case where multiple cracks develop in the matrix.     

Interaction effects among cortical bone, cancellous bone, and periodontal membrane of natural teeth and implants

Following the initial successes of Goldberg and Gershkoff (Dental Digest, 5, 11, 1947) with the placement of subperiosteal implants, interest in all types of implants emerged. As an aid to the evaluation of various designs and materials without resorting to clinical testing, finite element analyses are being conducted by a number of researchers to determine the stress system induced in bone. The present study investigates the effects of variation in the thicknesses of the periodontal membrane and cortical bone and of the model boundary on the stresses developed around a natural tooth or a tooth-shaped implant. The results show that strong effects due to the variation in these parameters can be expected. As a consequence, the problem of the analysis of any single implant must consider additional factors. These can influence overall implant design and may eventually help to explain what could appear as anomalies in clinical test results.     

Monoradiculopathy of the fifth lumbar nerve root due to lumbar disc herniation between lumbar one and lumbar two vertebrae

Mitochondrial mutations are associated with a wide spectrum of human diseases. A common class of point mutations affects tRNA genes, and mutations in the tRNA-leu(UUR) gene (MTTL1) are the most frequently detected. In earlier studies, we showed that lung carcinoma cybrid cells containing high levels (greater than 95%) of mutated mtDNA from a patient with the pathological nucleotide pair (np) 3243 tRNA-leu(UUR) mutation can remain genotypically stable over time, and exhibit severe defects in mitochondrial respiratory metabolism. From such a cybrid containing 99% mutated mtDNA, we have isolated a spontaneous derivative that retains mutant mtDNA at this level but which has nevertheless reverted to the wild-type phenotype, based on studies of respiration, growth in selective media, mitochondrial protein synthesis and biogenesis of mitochondrial membrane complexes. The cells are heteroplasmic for a novel anticodon mutation in tRNA-leu(CUN) at np 12300, predicted to generate a suppressor tRNA capable of decoding UUR leucine codons. The suppressor mutation represents approximately 10% of the total mtDNA, but was undetectable in a muscle biopsy sample taken from the original patient or in the parental cybrid. These results indicate that the primary biochemical defect in cells with high levels of np 3243 mutated mtDNA is the inability to translate UUR leucine codons.     

The effect of pamidronate on lumbar spine bone density and pain in osteoporosis secondary to systemic mastocytosis

Orthotopic liver transplantation (OLT) in patients infected with hepatitis B virus (HBV) is known to be associated with a high recurrence rate and poor prognosis. Interferon treatment in these patients offers little benefit and may lead to further complications. Lamivudine, the (-)enantiomer of 3'-thiacytidine, a 2'3'-dideoxynucleoside, is known to be a potent inhibitor of HBV replication in patients with chronic HBV infection. Three HBV-positive OLT patients were administrated lamivudine, 100 mg x 1 orally, for a period of at least 20 weeks, in an open, compassionate-use basis. All three patients were HBV DNA-negative before OLT. HBV reinfection occurred at a median time of 7 months (range, 6-9 months) after OLT, in spite of adequate immunoprophylaxis. All three patients had high serum transaminase levels (alanine aminotransferase [ALT], 103-324 U/L) and histologic evidence of recurrent HBV infection of the grafted liver, and HBV DNA was evident in the sera of all of them. Six weeks after lamivudine treatment, HBV DNA disappeared from the serum of all patients (detected by hybridization); by the 10th week, HBV DNA was also negative by polymerase chain reaction in two out of three patients. Interestingly, the one patient who was HBV DNA positive by polymerase chain reaction still has mildly elevated ALT levels, whereas the other two patients have normal ALT levels. We also noted that on the 5th week there was a transient elevation of serum ALT levels in two patients. No adverse effects or rejection episodes were noted. In conclusion, lamivudine is a beneficial and well-tolerated therapy in OLT patients with recurrent HBV infection. We are studying the effect of lamivudine in other patients and for a longer period of time.     

Influence of osteophytic size on bone mineral density measured by dual X-ray absorptiometry

Eight of the first 15 patients with advanced Parkinson's disease who underwent microelectrode guided posteroventral pallidotomy developed transient abnormal involuntary movements during thermolesion, four of whom also did so during high frequency macrostimulation. Abnormal involuntary movements found before thermolesion were choreic, ballistic, or choreoathetoid in nature, usually persisted less than 60 minutes, and were contralateral to the site of thermolesion in six and bilateral in two of them. The appearance of abnormal involuntary movements during macrostimulation or thermolesion of the internal globus pallidus correlated with better surgical outcome as measured by UPDRS motor items and CAPIT timed test, so that they seem to be of prognostic value.     

Accuracy of single-energy quantitative computed tomography in the assessment of bone mineral density of cervical vertebrae

Earlier studies have shown that single-energy quantitative computed tomography (SEQCT) is a reliable method for bone mineral density (BMD) measurements in thoracic and lumbar vertebrae. Moreover, SEQCT has proved to be a useful parameter in the selection of appropriate implants in cervical spondylodesis. The aim of this study was to determine the accuracy of SEQCT in cervical vertebrae BMD measurement. BMD with reference to calcium hydroxyapatite (Ca10[PO4]6[OH]2) was assessed by SEQCT in 100 human vertebral bodies of the cervical spine. Bone cylinders were then cut from the appropriate region of interest. The cylinder volume was determined by the liquid displacement technique. The density of the mineral component was measured following incineration at 1100 degrees C for 24 h. The calculated BMD was correlated with the SEQCT values, resulting in a coefficient of r = 0.79 (P < 0.01). Mean SEQCT values were significantly lower than those determined by direct density assessment (t-test for coupled sampling, P < 0.02). This result was in agreement with studies on thoracic and lumbar vertebrae. These data suggest that SEQCT can reliably measure BMD in the cervical spine.     

单压下节理密度及倾角对类岩石试件强度及变形的影响

通过预制张开节理类岩石试件,在单轴压缩条件下,研究节理密度及倾角的组合作用对试件强度和变形特征的影响.试验结果表明:(1)随着节理倾角的增大,应力-应变曲线由多峰值转变为单峰值,试件脆性增强,延性减弱;(2)节理密度对当量峰值强度的影响与节理倾角大小有关,对当量弹模的影响呈“V”形变化,即当量弹模随着节理密度的增大呈现先减小后增大的变化规律;(3)当量弹模随节理倾角的增大而增大,在节理倾角为90°的时候达到最大值,为完整试件弹性模量的70%~80%;(4)节理倾角对多节理类岩石试件当量峰值强度和当量弹性模量的影响大于节理密度的影响.对试验结果进一步分析发现:节理密度及节理倾角与应力-应变曲线、当量峰值强度及当量弹性模量之间的关系,其变化规律与试件的破坏过程息息相关,其破坏模式可分为张拉破坏、剪切破坏和复合破坏.     

Which vertebrae should be assessed in diagnosing osteoporosis by plain radiography? Comparative study of radiographic findings and bone mineral density measured by dual energy X-ray absorptiometry

OBJECTIVE: To determine rates of hospitalisation of young children for acute gastroenteritis in Australia, and to estimate the proportion of these admissions caused by rotavirus infection. DESIGN: Analysis of hospital admission records, and parallel, prospectively collected data on rotavirus-positive admissions. SETTING: Hospitals admitting young children in all Australian States and Territories in 1993-1996. PATIENTS: All children under five years admitted to hospital for acute gastroenteritis (International Classification of Diseases, ninth revision principal diagnosis codes 003.0, 004.0-009.3 and 558.9). MAIN OUTCOME MEASURES: Rate of hospital admission per 1000 children per year by State, and the proportion of admissions caused by rotavirus infection. RESULTS: There were almost 20,000 hospital admissions annually in Australia for acute gastroenteritis in children under five years, at an average rate of 15/1000. An estimated 50% of these were attributable to rotavirus infection, implying a rate of hospitalisation for rotavirus-related gastroenteritis of 7.5/1000/year. Among children under two years this rate was 11.6/1000. Rotavirus incidence rates generally followed a typical seasonal pattern in temperate regions of the country, with sharp peaks in mid to late winter. Rates of hospitalisation varied markedly, even between States with apparently similar patterns of disease, while the incidence in the Northern Territory was 3-5 times higher than other States. CONCLUSIONS: Rotavirus-related gastroenteritis is a major cause of hospital admissions in young children, and large savings to the healthcare system are possible if it can be prevented at reasonable cost. Variation in treatment practices between States may be worth studying in greater detail as another source of potential savings.     

The surgical treatment of disorders in the formation and fusion of the lumbar vertebrae in children

OBJECTIVE: To investigate the value of polymerase chain reaction (PCR) for follow-up patients infected by Chlamydia trachomatis. METHODS: Follow-up specimens were collected from 30 patients. Chlamydia trachomatis positive were detected by PCR and direct fluorescence assay test (DFA) in the 30 patients before therapy. 15 patients were treated with minocycline (100 mg twice daily) for 10 days, and 15 patients were treated with 1.0 g of azithromycine as a single oral dose. RESULTS: After 1-2 weeks of antimicrobial therapy, all patients had negative DFA for Chlamydia trachomatis, but 9 had positive Chlamydia trachomatis DNA as detected by PCR. CONCLUSIONS: The 9 specimens were not confirmed to livae viable organisms of Chlamydia trachomatis. The debris of nonviable Chlamydia trachomatis DNA was excluded from urinogenital tract at about one month.     

Determinants of radial bone density as measured by PQCT in pre- and postmenopausal women: the role of bone size

OBJECTIVE: To investigate characteristics of children and adolescents with a history of combined pharmacotherapy (CPT) and compare them with a group with no history of CPT. METHOD: Eighty-three consecutive admissions to a residential treatment center were divided into a CPT and a no-CPT group based on treatment history and compared by chart review. Prevalence of lifetime psychiatric medication use and CPT exposure were assessed. Demographic, diagnostic, treatment, behavioral, and medication variables were compared across the two groups. RESULTS: Medication use was present in the treatment history for 89.2% and a history of CPT was found for 60.3% of subjects. Admission to current placement from inpatient psychiatry, lifetime number of psychiatric placements, lifetime number of psychiatric diagnoses, and nonseizure neuropsychiatric comorbidity were significantly associated with CPT. Aggression and neuroleptic use were also significantly associated with CPT. Admission psychiatric diagnostic comorbidity was not associated with CPT. CONCLUSIONS: A high prevalence of psychiatric medication use and CPT was found in this population. Variables assessing illness severity, aggressive behavior, and nonseizure neuropsychiatric comorbidity may identify youths in psychiatric treatment settings with a high prevalence of past or current CPT exposure. Further research on the CPT of aggression is warranted.     

润滑条件对热力模拟压缩试验变形行为影响的数值模拟研究

针对热模拟压缩变形试验中的模具与材料之间的润滑情况即二者之间的面摩擦因数对试验的影响,使用数值模拟方法进行了研究,考察了不同摩擦因数对于压缩试验中的变形抗力、变形后试样应变分布和应变速率分布的影响。结果表明,摩擦因数对载荷力也就是应力—应变曲线没有显著影响,而对应变和应变速率的分布则有较大影响,会导致试样变形不均匀。     

Correlation relations between the parameters of the empirical dependences of some strength and diffusion characteristics on test conditions

Experimental data are often approximated by two-parameter relations in the form of a power or an exponential function. When a number of similar objects are considered, the parameters of these relations are connected by a correlation dependence. The examples of empirical relations where this dependence is observed are considered. In all cases of this correlation dependence, the value of an approximating function changes by several orders of magnitude when its argument varies by several times, and the initial data for the calculation of the empirical-equation parameters are located in a relatively narrow band in the coordinate space. This behavior is always accompanied by a linear relationship between the empirical coefficients of the equations obtained for a number of similar objects.     

测试条件对汽车高强钢扩孔率的影响

钢材的扩孔性能一般可用扩孔试验求出的扩孔率来评价,同种材料,由于试验条件的不同,测得的扩孔率存在显著差别。研究了不同的孔加工方式及毛刺朝向对扩孔率的影响,钻孔方式获得的扩孔率高于冲压孔方式获得的扩孔率,毛刺朝向与凸模运动方向相反时冲压孔获得的扩孔率,大于毛刺朝向与凸模运动方向相同时的冲压孔获得的扩孔率。