Blood circulation of long bones in trained growing rats and mice.

The effect of physical training on the blood circulation of long bones was studied in growing rats and mice of NMRI-strain. The animals to be trained and their controls were about 2 weeks old at the beginning of the training. The training took place on a 5 degree inclined treadmill 5 days a week for 3 weeks in experiment I and 7 weeks in experiments II and III. The duration of the daily exercise was progressively increased over 3 weeks. The final exercise bouts were 80 min for moderate and 180 min for intensive training programs. The circulating red cell volume (ml/100 g bone) of the humeral, femoral and tibial bones of the trained animals was lower compared to the controls in all three experiments mainly due to reduced hematocrit values. The circulating blood volume (ml/100 g bone) decreased in the tibial bones of the trained animals in experiment I and showed a decreasing tendency in experiment III, but no significant differences between the groups were observed in the humeral and femoral bones. Yet, when related to the volume of the bones the circulating blood volume (ml/100 ccm bone) was significantly higher in the femoral bones of the trained animals, while the changes in the humeral bones were negligible (experiment III). The results suggest that the vascularity of long bones is affected by physical training. The varying responses in different bones are perhaps due to the amount of mechanical stress during physical activity.     

A dynamic pattern of mechanical stimulation promotes ossification in avian embryonic long bones

We have performed a set of finite element analyses of embryonic chick hindlimb skeletal rudiments at several time points during development, around the time of initial bone formation. Using optical projection tomography, we created anatomically accurate rudiment and muscle morphologies for each stage. The changes in pattern and magnitude of biophysical stimuli (such as stress, strain, hydrostatic pressure and fluid flow) were computed, and were found to transform as bone formation proceeded in the rudiment. For each biophysical stimulus, a single concentration of the stimulus was predicted at the mid-diaphysis some time before initial bone formation begins. Then, several hours before ossification, two concentrations of the stimuli were predicted distal and proximal to the prospective bone collar. Once bone formation had begun, high concentrations of the stimuli were maintained proximal and distal to the bone collar. We propose the hypothesis that patterns of biophysical stimuli resulting from mechanical loading due to muscle contractions initiate and propagate ossification in avian embryonic long bones, whereby a region of the perichondrium experiences a period of time under high cyclic stimulus levels, promoting chondrocyte hypertrophy at the core and prompting bone collar formation some hours later.     

Sindbis-group alphavirus replication in periosteum and endosteum of long bones in adult mice

Several alphaviruses, including the Sindbis-group viruses, Ross River virus, O'nyong-nyong virus, and Chikungunya virus, are associated with outbreaks of acute and persistent arthralgia and arthritis in humans. Mechanisms underlying alphavirus-induced arthralgia and arthritis are not clearly understood, though direct viral replication within or around the affected joints is thought to contribute to disease. S.A.AR86 is a Sindbis-group alphavirus closely related to the arthralgia-associated Ockelbo and Girdwood S.A viruses. Following inoculation with S.A.AR86 derived from a molecular clone, infectious virus was isolated from bone and joint tissue 1 to 6 days postinfection. Studies using either in situ hybridization or S.A.AR86-derived double promoter viruses and replicons expressing green fluorescent protein localized sites of viral replication to the periosteum, tendons, and endosteum within the epiphyses of the long bones adjacent to articular joints. These results demonstrate that alphaviruses associated with arthralgia in humans replicate within bone-associated connective tissue adjacent to articular joints in an adult mouse model.     

Physical training and connective tissues in young mice: biochemistry of long bones

The effect of physical training on collagen, ground substance, and nucleic acid concentrations in long bones was studied in male mice of NMRI strain. The mice to be trained and their controls were about 2 wk old at the beginning of training, which took place on a 5 degrees inclined treadmill 5 days/wk for 3-22 wk. The duration of daily exercise was increased progressively over 3 wk. The final daily exercise bouts were 50 and 80 min for moderate programs and 180 min for the intensive program at a speed of 30 cm/s. Increased concentrations of nitrogen and hexosamines were found at both training intensities, especially after prolonged training. No conclusive changes in nucleic acid concentrations were observed after training. The hexosamine-hydroxyproline ratio was higher and the hydroxyproline-nitrogen ratio lower in the long bones of trained animals compared to the controls. In conclusion these data suggest that prolonged physical activity affects the organic matrix of long bones by maintaining above average concentrations of glycosaminoglycans in matured bones.     

Functional differentiation of long bones in lorises

The external dimensions of the limb bones and the geometry of their midshaft cross-sections were determined for Loris tardigradus and Nycticebus coucang. Relative cortical thickness, cortical area, and second moment of area were calculated and contrasted with locomotor stresses. The difference in shape-related strength of the bones between the smaller- and the larger-bodied species is more pronounced than can be expected from stresses acting during normal locomotion. The Nycticebus skeleton has a much higher safety margin overall and seems to be dimensioned for infrequent but critical stresses of high magnitude. Lorisine gaits in general are characterized by low ground reaction forces, great mobility in all joints, and a nearly equal share in propulsion and weight-bearing by the fore- and hindlimb. Accordingly, the long bones of lorises (especially those of L. tardigradus) tend to be less rigid than those of other mammalian species (including other primates), they lack a preferential plane of higher bending strength, and femur and humerus do not differ markedly in their capacity to withstand mechanical stresses. External dimensions of the humerus and femur of the two African lorisine species parallel and corroborate these results. Some more general implications for the relationships between bone shape and locomotor stresses are also discussed.     

Blood flow to long bones indicates activity metabolism in mammals, reptiles and dinosaurs

The cross-sectional area of a nutrient foramen of a long bone is related to blood flow requirements of the internal bone cells that are essential for dynamic bone remodelling. Foramen area increases with body size in parallel among living mammals and non-varanid reptiles, but is significantly larger in mammals. An index of blood flow rate through the foramina is about 10 times higher in mammals than in reptiles, and even higher if differences in blood pressure are considered. The scaling of foramen size correlates well with maximum whole-body metabolic rate during exercise in mammals and reptiles, but less well with resting metabolic rate. This relates to the role of blood flow associated with bone remodelling during and following activity. Mammals and varanid lizards have much higher aerobic metabolic rates and exercise-induced bone remodelling than non-varanid reptiles. Foramen areas of 10 species of dinosaur from five taxonomic groups are generally larger than from mammals, indicating a routinely highly active and aerobic lifestyle. The simple measurement holds possibilities offers the possibility of assessing other groups of extinct and living vertebrates in relation to body size, behaviour and habitat.     

An in vitro assay of bone development using fetal long bones of mice: morphological studies

The purpose of this study was to examine the morphological changes in an in vitro system in which the two elements of bone modelling, formation and resorption, could be studied simultaneously. Pregnant mice were killed on days 15, 16 and 17 of gestation, the fetuses were removed and the radii and ulnae dissected free of soft tissue. The bones were cultured for 6 days in media (BGJ) supplemented with 20% fetal calf serum and 150 micrograms/ml vitamin C. Growth and mineralization were estimated by measuring the total length of the bone, and diaphysis, and by light and transmission electron microscopy (TEM). The results of this study indicate that there is a continuous measurable increase in the total length of fetal mouse long bones over the 6 days of culture. These bones show a continuous growth of periosteal bone, with mesenchymal tissue penetrating into the diaphyseal shaft, and development of bone marrow like tissue. TEM examination showed differentiation of mesenchymal cells to osteoblasts, formation of new bone matrix and bone mineralization similar to that found in developmentally matched controls. In the cartilagenous epiphyses, however, many hydroxyapatite crystals were not associated with matrix vesicles. In addition, some of the chondrocytes of the hypertrophic zone appeared to be dedifferentiating into mesenchymal cells with osteoblast-like features. In spite of the lack of osteoclasts in the 15- and 16-day explants, osteoclasts appeared in the diaphysis after 2 and 4 days in culture. Our results suggest that this system can serve as a good model for the study of bone formation and resorption as they occur, simultaneously, during bone modelling.(ABSTRACT TRUNCATED AT 250 WORDS)     

Synostosis dynamics in human long tubular bones

More than 8,000 roentgenograms and electroroentgenograms of brachial, ulnar, radiocarpal, coxofemoral, knee, talocrural joints have been studied in persons of both sex at the age from birth up to 25 years. The synostosis degree is appreciated by the six-mark system. The roentgenological data are corroborate histologically. The method of appreciation applied makes it possible to reveal cases of initially forming synostosis long before puberty. Three stages of synostosis process are defined. The first stage--slow increase of the synostosis mark. The second--quick synostosis formation. The third--final stage. According to the stages defined, a comparative analysis of the synostosis process in all metaepiphyseal zones of all long tubular bones, peculiarities of the process depending on the sex are demonstrated. The data on the time, when the points of ossification appear, on the beginning and completion of synostosis process in all metaepiphyseal zones of the long tubular bones are presented.     

大熊猫取食竹笋期间的昼夜活动节律和强度

采用内置记录活动水平传感器的GPS项圈研究了卧龙自然保护区3只野生大熊猫春季取食竹笋期间的昼夜活动节律和强度,并分析了太阳辐射、温度因子对大熊猫活动节律与强度的影响。3只大熊猫的平均活动率为68.05%,受孕雌性大熊猫的活动率(70.86%)和活动强度(范围:0-255;水平方向/垂直方向,23.82±0.30/ 17.63±0.22)均比其它两只大熊猫(70.55%, 14.71±0.17/13.52±0.15 ;62.76%,17.74±0.23/13.61±0.18)高。大熊猫有3次活动高峰,分别出现在6:00-7:00,18:00-21:00和23:00-3:00,一个明显的活动低谷,出现在9:00-12:00。大熊猫白天的活动率(68.32%)和活动强度(19.59±0.20/ 15.45±0.15)比夜间(67.67%,17.63±0.19/14.21±0.15)高。大熊猫的活动强度与太阳辐射之间存在显著负相关(r=-0.822, P<0.001),与空气温度之间不存在显著的相关性。     

骨生苔藓在中国的新记录(英文)

在四川省马边大风顶国家级自然保护区的高山草甸上发现了生长在牦牛骨头上的苔藓。共有四种藓类植物:真藓科的真藓、刺叶真藓、丛藓科的短叶小石藓以及葫芦藓科的中华葫芦藓,它们都是顶蒴藓类。这是骨生苔藓植物在中国的首次记录报道。     

Estimation of torsional rigidity in primate long bones

Comparative studies of long bone biomechanics in primates frequently use the polar moment of inertia (J ) as a variable reflecting overall mechanical rigidity, average bending rigidity, or resistance to torsional shear stresses. While the use of this variable for characterizing the first two properties is appropriate, it is potentially a highly misleading measure of torsional resistance. Errors result from violations of assumptions required for the use of the polar moment of inertia; in particular, the predictive utility of J diminishes with departures from axial symmetry (i.e., a cylindrical cross-sectional shape). The magnitude of these errors is estimated both theoretically and experimentally. It is argued that the use of the polar moment of inertia for estimating long bone torsional rigidity should be restricted to samples of relatively invariant and/or cylindrical geometry. Alternative measures for torsional resistance are evaluated and reviewed.     

The epiphyseal cartilage and growth of long bones in Rana catesbeiana.

The structure of the epiphyseal cartilage of the bullfrog Rana catesbeiana and its role in the growth of long bones were examined. The epiphyseal cartilage was inserted into the end of a tubular bone shaft, defining three regions: articular cartilage, lateral articular cartilage and growth cartilage. Joining the lateral cartilage to the bone was a fibrous layer of periosteum, rich in blood vessels. Osteoblasts with alkaline phosphatase activity were found on the surface of the periosteal bone, which presented a fibrous non-mineralised tip. The growth cartilage was inside the bone. The proliferative chondrocytes presented perpendicular separation of daughter cells and there was no columnar arrangement of the cells. Furthermore, chondrocyte hypertrophy was not associated with either calcification or endochondral ossification, in apparent contrast to the avian and mammalian models. Finally, there was no reinforcement system capable of directing cell volume increase into longitudinal growth. Since bone extension depends on the intramembranous ossification of the periosteum, the growth cartilage is inside and not at the end of the bone and the cells in the growth cartilage show no columnar arrangement and separate in a direction perpendicular to the long bone axis, we conclude that the growth cartilage mainly contributes to the radial expansion of the bone.