[Nitrogen metabolism and secondary metabolism regulation of Atropa belladonna by exogenous NO under NaCl stress].

Atropa belladonna seedlings were used as experimental materials and cultivated by soil culture method. Different concentrations(0,0.05,0.1,0.2,0.5 mmol·L~(-1))of NO donor sodium nitroprusside(SNP) were sprayed on the leaves. The effects of different concentrations of SNP and different treatment time(4,8,12,16 d) on nitrogen metabolism, secondary metabolite content, precursor content of tropane alkaloid synthesis pathway and expression of key enzyme genes under 100 mmol·L~(-1) NaCl stress were studied. The results showed that with the prolongation of salt stress, the nitrogen metabolism and the accumulation of secondary metabolites of A. belladonna were inhibited to some extent. After treatment with different concentrations of exogenous SNP, the ammonium nitrogen content decreased dramatically, and the contents of nitrate nitrogen, free amino acid, soluble protein and the activities of key enzymes of nitrogen metabolism(NR, GS, GDH) were all greatly improved; the contents of precursor amino acids(ornithine, arginine) and polyamines(Put, Spd, Spm) in the secondary metabolic pathway have increased to varying degrees. The qRT-PCR analysis showed that exogenous SNP treatment can effectively promote the high expression of key enzyme genes PMT, TRⅠ and H6H in the secondary metabolic pathway of A. belladonna, and the production of hyoscyamine and scopolamine were increased notably. In summary, the application of appropriate concentration of SNP can effectively alleviate the inhibition of salt stress on the nitrogen metabolism and secondary metabolism of Atropa belladonna, and enhance its salt tolerance. Overall, 0.1 mmol·L~(-1) and 0.2 mmol·L~(-1) SNP treatment achieved the most remarkable effect.

Evaluation of unicondylar knee arthroplasty and fibulectomy from a biomechanical viewpoint / 医用生物力学

Varus deformation in knee joint is one of the common symptoms caused by unicompartment knee osteoarthritis. Currently, several operations can be used for correcting such deformation, including high tibial osteotomy, unicondylar knee arthroplasty (UKA) and fibulectomy. UKA has been developed for over 60 years, with the advantage of normal knee kinematics restored, less incision, more bony tissue preserved and larger range of motion than total knee arthroplasty (TKA). Therefore, UKA has become a reliable method for treating unicompartment knee osteoarthritis. Fibulectomy is a new kind of surgical technique for treating varus deformation in knee joint, with the advantage of simple operation, low cost and fast recovery. At present, fibulectomy has been widely applied, but its treatment mechanism is still not clear. In this review, two clinical operations UKA and fibulectomy were summarized, and the possible mechanism of fibulectomy for treating unicompartment knee osteoarthritis was proposed from the viewpoint of biomechanics. The author hypothesized that reduction in lateral muscle force after fibulectomy would cause rebalance of the resultant joint moment, therefore, the change of joint contact position and the decrease in joint contact force might be the cause of fibulectomy to release the pain for knee osteoarthritis patients.

Regularity on change of retinal nerve fiber layer thickness with acute high intraocular pressure / 医用生物力学

Objective To measure the rabbit retinal nerve fiber layer(RNFL) thickness in vivo under different intraocular pressures (IOP) and at different time intervals after acute high IOP, and to obtain the regularity on change of RNFL thickness with acute high IOP. Methods Four groups of acute high IOP model were formed by perfusing the saline water into the anterior chamber of rabbit eyes, then RNFL thickness under different IOPs was measured by optical coherence tomography with radial scanning mode whose center was optical papilla and diameter was 6 mm. Results The absolute change values of RNFL thickness were(-27.16±14.24), (-33.33±6.74), (-48.75±5.24), (-67.29±3.89) μm under different IOPs of (4.50±0.35), (6.07±0.31), (7.74±0.26), (10.71±0.07) kPa, respectively. The linear relationship was found between the relative change of RNFL thickness and IOP. IOP could return to the normal level within two days after acute high IOP, while the RNFL thickness could be restored at the second week, and it was easier to restore if the IOP was lower than 6.65 kPa. Conclusions The acute high IOP could cause RNFL thickness to decrease significantly with the increased acute high IOP, but it will be restored after some time.