The osteogenic response to distant skeletal injury

We tested the hypothesis that when one bone of the skeleton is injured, others experience an osteogenic response. Although similar or related phenomena have been observed previously, the purposes of the study were to determine if this response was reproducible, to characterize it in terms of its magnitude and duration, and to show how it is related to the type of injury sustained. To obtain this information, a model was used in which an intramedullary nail was implanted in the femur and a standard closed fracture was subsequently produced. The osteogenic response was measured by histomorphometry. Eight-four nine-week-old male Sprague-Dawley rats were divided into seven groups of twelve animals each. Groups I and II consisted of control animals in which no injury was produced. In Group-III rats, cortical drilling of the intercondylar notch and piriformis fossa of the right femur was performed, without intramedullary nailing. In Groups IV through VII, half of each group received intramedullary nails only, and in the other half intramedullary nailing was done and a closed transverse diaphyseal fracture was produced. With two different fluorochrome labels, rates of mineral apposition were measured in the left and right tibiae of all animals. The labeling periods differed in each group and were designed to determine when the peak response occurred, how long it lasted, and whether aging during the course of the experiment affected the response.(ABSTRACT TRUNCATED AT 250 WORDS)     

阳、阴离子型药物电位滴定通用电极的比较研究

磷钨酸十六烷基三辛基铵电极可用于多种阳离子型及阴离子型药物的电位滴定,分别用四苯硼钠及硫酸作滴定剂,电位突跃可达150～400 mV,最低测定浓度可达10^-5mol/L左右,经过短时转化,即可改用于不同药物的滴定。季磷、季钟盐型电极或其它阴离子型电极性能较差。电活性物显示烃基加重效应。电极结构无显著影响。表面活性剂苯扎溴铵可加速活化。     

A member of a family of sulfate-activating enzymes causes murine brachymorphism

Sulfation is critical to the function of a wide variety of biomolecules. This common modification requires the enzymatic synthesis of an activated sulfate donor, phosphoadenosine-phosphosulfate (PAPS). In higher organisms PAPS synthesis is catalyzed by a bifunctional sulfurylase kinase (SK) polypeptide having both ATP-sulfurylase and adenosine-phosphosulfate kinase activities. We report the identification of a gene family encoding murine SK proteins with these two activities. A family member, SK2, colocalizes with the locus for the autosomal recessive murine phenotype brachymorphism. Brachymorphic mice have normal lifespans, but abnormal hepatic detoxification, bleeding times, and postnatal growth, the latter being attributed to undersulfation of cartilage proteoglycan. A missense mutation in the SK2 coding sequence of bm mice that alters a highly conserved amino acid residue destroys adenosine-phosphosulfate kinase activity and therefore the ability of SK2 to synthesize PAPS. We conclude that a family of SK genes are responsible for sulfate activation in mammals, that a mutation in SK2 causes murine brachymorphism, and that members of this gene family have nonredundant, tissue-specific roles.     

CT of sacral injury

Eighty-eight patients with 188 sacral fractures were examined with computed tomography (CT) and conventional radiography. Four main patterns of sacral injury were defined: sacroiliac diastasis (39%), sacral and/or iliac lip fractures (25%), vertical shear fractures (25%), and comminuted fractures (5%). Initial interpretation of plain radiographs failed to define 29% of the sacroiliac joint diastases, 57% of the lip fractures, 34% of the vertical shear fractures, and 25% of the comminuted fractures. The extent of injury was better delineated with CT, and a more certain diagnosis of sacral injury was possible with CT than with radiography. Because of the higher detection rate and improved imaging of fracture configuration, CT should be performed in all patients with sacral injury.     

Evaluation of gene therapy for citrullinaemia using murine and bovine models

Citrullinaemia is an autosomal recessive disorder caused by the deficiency of argininosuccinate synthase. The deficiency of this enzyme results in an interruption in the urea cycle and the inability to dispose of excess ammonia derived from the metabolism of protein. The only treatment for this disorder has been dietary restriction of protein and supplementation with medications allowing for alternative excretion of excess nitrogen. Gene therapy offers the possibility of a long-term cure for disorders like citrullinaemia by expressing the deficient gene in the target organ. We have explored the use of adenoviral vectors as a treatment modality for citrullinaemia in two animal models, a naturally occurring bovine model and a murine model created by molecular mutagenesis. Mice treated with adenoviral vectors expressing argininosuccinate synthase lived significantly longer than untreated animals (11 days vs 1 day); however, the animals did not exhibit normal weight gain during the experiment, indicating that the therapeutic effectiveness of the transducing virus was suboptimal. It is speculated that part of the failure to observe better clinical outcome might be due to the deficiency of arginine. In the bovine model, the use of adenoviral vectors did not result in any change in the clinical condition of the animals or in the level of plasma ammonia. However, the use of ¹⁵N isotopic ammonia allowed us to assess the flux of nitrogen through the urea cycle during the experiment. These studies revealed a significant increase in the flux through the urea cycle following administration of adenoviral vectors expressing argininosuccinate synthase. We conclude that the use of adenoviral vectors in the treatment of citrullinaemia is a viable approach to therapy but that it will be necessary to increase the level of transduction and to increase the level of enzyme produced from the recombinant viral vector. Future experiments will be designed to address these issues.     

独活中欧芹酚甲醚和二氢山芹醇醋酸酯的HPLC法测定(英文)

本文从伞形科植物重齿毛当归(Angelica pubescens Maxim.f.biserrata Shan et Yuan)的干燥根中分离得主要成分欧芹酚甲醚(osthole)和二氢山芹醇醋酸酯(columbianetin acetate)。并以此为对照品,用反相HPLC法测定了独活药材中二者的含量。使用ZORBAXODS 4.6mm×15cm反相柱,甲醇一水(2:1)作流动相,280nm为检测波长,本法简便、快速,为独活的含量测定提供了分析方法。     

Lrp5-independent activation of Wnt signaling by lithium chloride increases bone formation and bone mass in mice

One of the well characterized cell biologic actions of lithium is the inhibition of glycogen synthase kinase-3beta and the consequent activation of canonical Wnt signaling. Because deficient Wnt signaling has been implicated in disorders of reduced bone mass, we tested whether lithium could improve bone mass in mice. We gavage-fed lithium chloride to 8-week-old mice from three different strains (Lrp5(-/-), SAMP6, and C57BL/6) and assessed the effect on bone metabolism after 4 weeks of therapy. Lrp5(-/-) mice lack the Wnt coreceptor low-density lipoprotein receptor-related protein 5 and have markedly reduced bone mass. Lithium, which is predicted to act downstream of this receptor, restored bone metabolism and bone mass to near wild-type levels in these mice. SAMP6 mice have accelerated osteoporosis due to inadequate osteoblast renewal. Lithium significantly improved bone mass in these mice and in wild-type C57BL/6 mice. We found that lithium activated canonical Wnt signaling in cultured calvarial osteoblasts from Lrp5(-/-) mice ex vivo and that lithium-treated mice had increased expression of Wnt-responsive genes in their bone marrow cells in vivo. These data lead us to conclude that lithium enhances bone formation and improves bone mass in mice and that it may do so via activation of the canonical Wnt pathway. Lithium has been used safely and effectively for over half a century in the treatment of bipolar illness. Prospective studies in patients receiving lithium should determine whether it also improves bone mass in humans.     

Fracture healing and osteocalcin metabolism in vitamin K deficiency

Osteocalcin (a vitamin K-dependent, bone-specific protein) is widely accepted as a marker of osteoblastic activity. The present study was conducted to determine if a vitamin K deficiency would affect fracture healing by virtue of an alteration in osteocalcin metabolism. Thirty male Sprague-Dawley rats were divided into two groups. The control group was fed a diet that was lacking in, but offered water replete with vitamin K. The experimental group was fed a vitamin K-deficient diet and was offered water that was lacking in vitamin K. After two weeks, vitamin K deficiency was established in the experimental group as shown by decreased urinary excretion of gamma-carboxyglutamic acid and an elevation of serum prothrombin times to between two to two and one-half times the control values. At this time, a standard, closed femoral fracture was produced. Six weeks later, the animals were killed. The bones were biomechanically tested in torsion. Subsequent to mechanical testing, the calluses were retrieved, and the osteocalcin content and the degree of gamma carboxylation of the osteocalcin in the calluses were measured. The results show that despite significant alterations in the gamma carboxylation of osteocalcin and elevation of prothrombin times to two to two and one-half times the control values, there were no differences in the mechanical properties of the calluses. Furthermore, there were no differences in the content or gamma carboxylation of osteocalcin in these calluses. Apparently, in vitamin K deficiency, fracture callus achieves normal mechanical properties and may have a mechanism for the gamma carboxylation of glutamic acids in osteocalcin despite a substantial depression of this activity in the rest of the body.