Effect of circular motion exercise on bone modeling and bone mass in young rats: an animal model of isometric exercise

The aims of the study are to develop a non-invasive animal model of circular motion exercise and to evaluate the effect of this type of exercise on bone turnover in young rats. The circular motion exercise simulates isometric exercise using an orbital shaker that oscillates at a frequency of 50 Hz and is capable of speeds from 0-400 rpm. A cage is fixed on top of the shaker and the animals are placed inside. When the shaker is turned on, the oscillatory movement should encourage the animals to hold on to the cage and use various muscle forces to stabilize themselves. Rats at 8 weeks of age were trained on the shaker for 6 weeks and static and dynamic histomorphometric analyses were performed for the proximal tibial metaphysis and the tibial shaft. The exercise resulted in no significant effect on animal body weight, gastrocnemius muscle weight and femoral weight. Although the bone formation rate of cancellous and cortical periosteum was increased by the exercise, trabecular bone volume was decreased. The exercise increased periosteal and marrow perimeters and the cross-sectional diameter of cortical bone from medial to lateral without a significant increase in the cortical bone area. These results suggest that circular motion exercise under force without movement or additional weight loading will cause bone-modeling drift with an increase in bone turnover to reconstruct bone shape in adaptation to the demand in strength. Since there is no additional weight loading during circular motion exercise, the net mass of bone is not increased. The bone mass lost in trabecular bone could possibly be due to a re-distribution of mineral to the cortical bone.     

DNA transfer by highly asymmetric somatic hybridisation in Medicago truncatula (+) Medicago rugosaand Medicago truncatula(+) Medicago scutellata

A regenerable line of Medicago truncatula (Jemalong 2HA) as a recipient species, was fused with the sexually incompatible species Medicago scutellata or Medicago rugosa. The treatments described maintain the chromosome number of the recipient but enable the transfer of small amounts of DNA of the donor species, probably by intergenomic recombination. Without a chromosome number-change fusion products can readily regenerate to produce fertile plants; and potentially a library with a diverse array of new genetic material. The selection of fused cells is based on treatment of the recipient cells with iodoacetamide (IOA), a non-regenerable donor, γ-irradiation of the donor, and regeneration on a medium favouring the recipient. DNA transfer was demonstrated by amplified fragment length polymorphism (AFLP), Southern hybridisation and changed morphology. Received: 21 December 2000 / Accepted: 5 April 2001     

A ribosome-free extract from cultured cells improves recovery of polysomes from the mosquito fat body: analysis of vitellogenin and ribosomal protein rpL34 gene expression

We have examined the association of ribosomal protein rpL34 mRNA with polysomes in Aedes albopictus C7-10 cells in culture using a simple, two-step sucrose gradient. In growing cells, 40-50% of the ribosomes were engaged on polysomes. This proportion could be increased to 80% when metabolism was stimulated by refeeding the cells with fresh medium. Conversely, ribosomes shifted off polysomes when cells were starved with phosphate-buffered saline or cell lysates were treated with puromycin. When similar approaches were used with fat body from blood-fed female Aedes aegypti mosquitoes, we were unable to obtain the polysome fraction that contained vitellogenin mRNA, which is abundantly translated after a blood meal. Addition of post-mitochondrial supernatant from fat body to polysomes from cultured cells shifted the polysome profile towards smaller polysomes and monosomes, in a dose-dependent fashion. Disruption of fat body tissue in a post-ribosomal supernatant from refed cells improved the recovery of polysomes, demonstrating both the engagement of vitellogenin mRNA on polysomes and the mobilization of rpL34 from messenger-ribonuceloprotein particles onto polysomes in blood-fed mosquitoes. These observations suggested that ribonucleases remain active when polysomes are prepared from mosquito fat body, and that cell culture supernatant contains a ribonuclease inhibitor.     

A novel noncollagenous protein encoded by an alternative transcript of the chick type III collagen gene is expressed in cartilage,bone and muscle

RanBP1, a velocardiofacial syndrome/DiGeorge syndrome candidate gene, is expressed in the frontonasal processes, branchial arches, aortic arches, and limb buds. At these sites, RanBP1 apparently coincides with neural crest-derived mesenchymal cells. In addition, RanBP1 is expressed in the forebrain as well as in hindbrain regions previously associated with crest-derived mesenchymal cells.     

蛋白酶活化受体-2的研究进展

蛋白酶活化受体(protease-activated receptors,PARs)属于G蛋白偶联受体家族成员,其N-末端被蛋白酶裂解后,可形成新的N-末端。新N-末端能够结合、激活自身受体。PAR-2是PARs的成员之一,其激活、灭活、脱敏、复敏、及其与信号转导途径的关系,尤其是与疾病(如呼吸道慢性炎症)的关系正倍受关注。     

Membrane permeability of fructose-1,6-diphosphate in lipid vesicles and endothelial cells

Fructose-1,6-diphosphate (FDP) is a glycolytic intermediate which has been used an intervention in various ischemic conditions for two decades. Yet whether FDP can enter the cell is under constant debate. In this study we examined membrane permeability of FDP in artificial membrane bilayers and in endothelial cells. To examine passive diffusion of FDP through the membrane bilayer, L-a-phosphatidylcholine from egg yolk (Egg PC) (10 mM) multi-lamellar vesicles were created containing different external concentrations of FDP (0, 0.5, 5 and 50 mM). The passive diffusion of FDP into the vesicles was followed spectrophotometrically. The results indicate that FDP diffuses through the membrane bilayer in a dose-dependent fashion. The movement of FDP through Egg PC membrane bilayers was confirmed by measuring the conversion of FDP to dihydroxyacetone-phosphate and the formation of hydrozone. FDP (0, 0.5, 5 or 50 mM) was encapsulated in Egg PC multilamellar vesicles and placed in a solution containing aldolase. In the 5 and 50 mM FDP groups there was a significant increase in dihydroxyacetone/hydrazone indicating that FDP crossed the membrane bilayer intact. We theorized that the passive diffusion of FDP might be due to disruption of the membrane bilayer. To examine this hypothesis, small unilamellar vesicles composed of Egg PC were created in the presence of 60 mM carboxyfluorescein, and the leakage of the sequestered dye was followed upon addition of various concentrations of FDP, fructose, fructose-6-phosphate, or fructose-1-phosphate (0, 5 or 50 mM). These results indicate that increasing concentrations of FDP increase the leakage rate of carboxyfluorescein. In contrast, no concentration of fructose, fructose-6-phosphate, or fructose-1-phosphate resulted in any significant increase in membrane permeability to carboxyfluorescein. To examine whether FDP could pass through cellular membranes, we examined the uptake of ¹⁴C-FDP by endothelial cells cultured under hypoxia or normoxia for 4 or 16 h. The uptake of FDP was dose-dependent in both the normoxia and hypoxia treated cells, and was accompanied by no significant loss in endothelial cell viability. Our results demonstrate that FDP can diffuse through membrane bilayers in a dose-dependent manner.     

Quantitative proteomics of pomegranate varieties with contrasting seed hardness during seed development stages

In pomegranate (Punica granatum), seed hardness is an important trait directly affecting fruit marketability. However, seed formation in pomegranate has not been well studied. We investigated the genetic mechanism underlying pomegranate seed hardness by comparing protein expression profiles between soft- and hard-seeded varieties 60 and 120 days after flowering. We identified 1940 proteins, of which 399 were differentially expressed. Most of the differentially expressed proteins were involved in posttranslational modification and carbohydrate metabolism. Cell wall biosynthesis, which showed positive correlations with seed hardness, was selected as the candidate pathway. The mRNA levels of 14 proteins involved in cell wall biosynthesis were further analyzed by qPCR. Lignin biosynthesis-related differentially expressed proteins showed lower expression at protein and gene levels in a soft-seeded variety at the early stages. Moreover, cellulose biosynthesis-related differentially expressed proteins showed higher expression levels in the soft-seeded variety at 60 days after flowering. Thus, the soft-seeded variety showed lower lignin but higher cellulose biosynthesis at the early fruit developmental stage, suggesting that lignin and cellulose play opposing roles in cell wall formation in pomegranate seeds. Moreover, differentially expressed proteins involved in cell wall degradation showed higher expression levels in the soft-seeded variety at both developmental stages. These results suggested that differences in seed hardness between soft- and hard-seeded pomegranates might result from cell wall biosynthesis and also be affected by cell wall degradation. The present proteome-wide profiling of pomegranate genotypes with contrasting seed hardness adds to the current knowledge base of the molecular basis of seed hardness development.