The effects of high dose of parathyroid hormone on fetal osteoclasts and their precursors in vivo: An ultrastructural-cytochemical study

Background: It is not well known how the immediate precursors of osteoclast develop into osteoclasts in the fetus. This ultrastructural-cytochemical study was designed to clarify the formation process of the osteoclasts and their increased activities in the fetal mouse limb buds after administration of high dose parathyroid hormone (PTH). Methods: Twenty-four or forty-eight hours after the high doses of PTH were injected into amniotic fluid of the pregnant C₃H mice, the femoral limb buds of embryos were dissected out. Tartrate-resistant acid phosphatase (TRAP) reactions were performed while preparing specimens for electron microscopy. Results: Both control and PTH-given preosteoclasts and osteoclasts exhibited TRAP-positivities in dense bodies and vesicles. As effects of PTH, a binucleated preosteoclast of tandem fashion was observed. More osteoclastic hyperactivities were observed in the diaphyseal bone marrow. An osteoclast with a large cytoplasm exhibited two sets of clear zones and ruffled borders. Some osteoclasts demonstrated prominent amoeboid figures, while other osteoclasts developed large cytoplasmic vacuoles, which contained pieces of calcified chondroid bars. Conclusions: Our results revealed the progression of maturation from young preosteoclasts to osteoclasts. An existence of a peculiar binucleated preosteoclasts suggested one of the processes for multinucleation of the osteoclast. Quite remarkable osteoclastic hyperactivities were obviously the effects of high dose PTH. Our results also indicated the endophagocytic ability of the osteoclast. How PTH affected the osteoclasts and their precursors in the diaphyseal bone marrow can be speculated. © 1995 Wiley-Liss, Inc.     

The dynamics of isometric bimanual coordination

Eight right-handed subjects performed rhythmic isometric applications of torque in the directions of pronation and supination of the forearm, in single limb and bimanual conditions. Bimanual movements were executed in either in-phase (homologous muscles simultaneously active) or anti-phase (non-homologous muscles active simultaneously) modes of coordination, in self-paced and frequency-scaled conditions. In the inphase (frequency-scaled) condition, subjects were required to synchronise (applications of torque) with each beat of a metronome, either in the direction of pronation or supination. In the anti-phase (frequency-scaled) condition, subjects were required to synchronise (applications of torque) with each beat of the metronome, either to the left or to the right. Departures from the anti-phase mode of coordination were observed as pacing frequency was increased. However, these departures were of short duration and the anti-phase mode was always re-established. These findings are in marked contrast to those obtained when there is free motion of the limbs. There also existed systematic differences between the stability of the pronation and supination phases of torque application. These differences were, in turn, modified through coincidence with the pacing signal. These results are discussed with reference to the constraints imposed upon the coordination dynamics by the intrinsic properties of the neuromuscular-skeletal system.     

Control strategies in directing the hand to moving targets

Summary We have evaluated the use of visual information about the movement of a target in two tasks tracking and interceptions — involving multi-joint reaching movements with the arm. Target velocity was either varied in a pseudorandom order (random condition) or was kept constant (predictable condition) across trials. Response latency decreased as target velocity increased in each condition. A simple model that assumes that latency is the sum of two components — the time taken for target motion to be detected, and a fixed processing time — provides a good fit to the data. Results from a step-ramp experiment, in which the target stepped a small distance immediately preceding the onset of the ramp motion, were consistent with this model. The characteristics of the first 100 ms of the response depended on the amount of information about target motion available to the subject. In the tracking task with randomly varied target velocities, the initial changes in hand velocity were largely independent of target velocity. In contrast, when the velocity was predictable the initial hand velocity depended on target velocity. Analogously, the initial changes in the direction of hand motion in the interception task were independent of target velocity in the random condition, but depended on target velocity in the predictable condition. The time course for development of response dependence was estimated by controlling the amount of visual information about target velocity available to the subject before the onset of limb movement. The results suggest that when target velocity was random, hand movement started before visual motion processing was complete. The response was subsequently adjusted after target velocity was computed. Subjects displayed idiosyncratic strategies during the catch-up phase in the tracking task. The peak hand velocity depended on target velocity and was similar for all subjects. The time at which the peak occurred, in contrast, varied substantially among subjects. In the interception task the hand paths were straighter in the predictable than in the random condition. This appeared to be the result of making adjustments in movement direction in the former condition to correct for initially inappropriate responses.     

Limb preference after unilateral pyramidotomy in adult and neonatal rats

As previously reported, unilateral pyramidotomy in newborn rats results in the development of an aberrant ipsilateral corticospinal tract that originates from the intact side. In the present study, limb preference after unilateral pyramidotomy in adult and neonatal rats was examined in search of differences that might correlate with this aberrant tract. However, no significant differences were observed between the two groups. Postoperatively, adult animals preferred the limb corresponding to the intact corticospinal tract in spite of a pre- and postoperative testing bias toward the opposite limb. Similarly, the animals that sustained neonatal lesion followed by testing at maturity also preferred the limb corresponding to the normal crossed corticospinal tract.     

Inhibition of prostaglandin synthesis reduces cyclic AMP levels and inhibits chondrogenesis in cultured chick limb mesenchyme

The present study investigated effects of inhibiting the synthesis of prostaglandins (PGs) on cyclic AMP concentrations and chondrogenesis in cultured chick limb mesenchyme. Indomethacin produced concentration-dependent inhibition of both PGE₂ synthesis and chondrogenesis over a concentration range of 50--200 M. Half maximal inhibition of PGE₂ was achieved with 50 M concentrations of the drug which also produced visibly reduced amounts of cartilage matrix in cell cultures as evaluated by Alcian green staining on day 6 of culture. The inhibitory effects of indomethacin on chondrogenesis were largely reversed by addition of 1 mM dibutyryl cAMP, indicating that cells could still respond to cyclic AMP stimulation. Endogenous levels of cyclic AMP, which increased by 6 fold during the six days of culture in control cells, did not increase significantly from dissociated cells at the time of plating (day 0) in indomethacin-treated cultures. The results indicate that inhibition of the prechondrogenic rise in PGE₂ concentrations in limb mesenchyme prevents the increase in cyclic AMP levels which occur during this same period resulting in inhibition of chondrogenesis. The data provide further support for the hypothesis that PGE₂, through its effects on the adenylate cyclase-cAMP system, plays an important role in the differentiation of cartilage.     

不同温度加热自体骨成骨活性的对比实验研究

目的研究加热对自体骨成骨活性的影响.方法通过手术造成家兔胫骨1cm的骨缺损,原位分别植入新鲜自体骨、加热100℃20min及50℃20min自体骨,于手术后2、4、8、12周进行X线摄片,并对平片的相对灰度进行分析,测定骨痂胶原蛋白的含量,并与组织学检查进行对比.结果新鲜自体骨成骨活性最高,其次是加热50℃20min自体骨,加热100℃20min自体骨成骨活性最差.结论加热影响植入骨的成骨活性,而较低温度加热可以保留一定的成骨活性.     

Successful 18-h acellular extracorporeal perfusion and replantation of porcine limbs - Histology versus nerve stimulation

The current standard for composite tissue preservation is static cold storage (SCS) and is limited to 6 h until irreversible muscle damage occurs. Extracorporeal perfusion (ECP) is a promising technique for prolonged preservation, however, functional results have been scarcely researched. This article assessed neuromuscular function and compared results to histological alterations to predict muscle damage after ECP. Forelimbs of twelve Dutch landrace pigs were amputated and preserved by 4 h SCS at 4–6 °C (n = 6) or 18 h mid-thermic ECP with University of Wisconsin solution (n = 6). Limbs were replanted and observed for 12 h. Sham surgery was performed on contralateral forelimbs (n = 12). Histology analysis scored four subgroups representing different alterations (higher score equals more damage). Muscle contraction after median nerve stimulation was comparable between ECP, SCS, and sham limbs (P = 0.193). Histology scores were higher in ECP limbs compared to SCS limbs (4.8 vs. 1.5, P = 0.013). This was mainly based on more oedema in these limbs. In-vivo muscle contraction was well preserved after 18 h ECP compared to short SCS, although histology seemed inferior in this group. Histology, therefore, did not correlate to muscle function at 12 h after replantation. This leads to the question whether histology or neuromuscular function is the best predictor for transplant success.     

Repair of cartilaginous fractures during chick limb development.

The embryonic chick wing has been used extensively in experimental analyses of the mechanisms involved in limb development. This study employs the embryonic wing in an examination of the possible origin of congenital pseudoarthrosis, a poorly understood limb disorder. To this end, chick radii were fractured in the middiaphysis prior to the onset of osteogenesis (6.5-7 days of incubation). The subsequent development of the fractured elements was examined using both whole mount preparations and histology. Callus cartilage did not form around any of the fractures. Nonetheless, the majority (29 of 33 specimens) of fractures united during primary osteogenesis (within 24-36 h of the operation), with bone formation occurring both across the fracture site and also over the cut ends of the cartilage. In addition, bones that exhibited a configuration similar to that described as giving rise to a type II congenital pseudoarthrotic condition were obtained. Typically, these bones showed an "hourglass" constriction midshaft and anterior bowing. These results suggest that the embryonic chick limb may serve as a useful experimental model system for the investigation of this congenital limb disorder.     

五氧化二钒的体外发育毒性研究

采用胚胎肢芽细胞进行原代微团培养 ,培养物经不同浓度的五氧化二钒 (V2 O5 )对细胞肢芽细胞经 5天增减形成细胞集落 ,V2 O5 对体外肢芽细胞的分化有明显抑制作用 ,并有较明显的剂量 -效应关系 ,其半数生长抑制浓度(ICV5 0 )和半分化抑制浓度 (ICD5 0 )分别为 12 .6和 1.6μg ml,V D值为 7.9。表明抑制细胞分化可能是V2 O5 致发育危害的重要作用机理