Tracer-based MRI evaluation on transportation and clearance in extracellular space of rats / 中国医学影像技术

Objective To explore the rule of transportation in extracellular space (ECS) and the changes induced by the external stimulation with tracer-based MRI.Methods Thirty two mature Sprague Dawley rats were randomly divided into four groups,i.e.caudate nucleus-control (Cc) group,thalamus-control (Tc) group,caudate nucleus-moving (Cm) group and thalamus pain stimulation (Tp) group.The rats were anesthetized and a series of MR scanning were performed before and after the injection of Gd-DTPA in ECS of caudate nucleus and thalamus until the intensity of Gd-DTPA was invisible.Half-life of Gd-DTPA in ECS was calculated and analyzed with t-test.Results Gd DTPA in caudate nucleus was transported to the ipsilateral cortices away from the injection points,which only distributed on site in the thalamus.The transportation between the two partitions was not observed.The half-life of Tc group ([49.93±2.11] min) was significantly shorter than that of Cc group ([104.30±54.12];t=2.839,P＜0.05),no difference was observed between the Cm group ([113.42±47.32]min) and Cc group (t=0.359,P＞0.05),while half-life of Tp group ([109.40±10.33]min) was significantly longer than that of Tc group (t=15.954,P＜0.05).Conclusion Tracer-based MRI can be used to investigate the rule of transportation in ECS,and the transportation and clearance of substances into the ECS can be influenced by a selective external stimulation.

Role of aquaporin-4 in the change of interstitial fluid drainage in Alzheimer's disease / 北京大学学报(医学版)

OBJECTIVE@#To observe the characteristics of the interstitial fluid (ISF) drainage in the Alzheimer's disease (AD) rats through magnetic resonance imaging (MRI) tracer gadolinium-diethylene triamine pentacetic acid (Gd-DTPA)spread in the brain extracellular space (ECS) and to discuss the role of aquaporin-4 (Aqp4) in the AD.@*METHODS@#Wild type SD rats (300-350 g) and Aqp4 gene knock out (Aqp4-/-) SD rats (300-350g) were divided into Sham group, AD group, Aqp4-/--Sham group and Aqp4-/--AD group. Sham group and Aqp4-/--Sham group were injected with saline by intraperitoneal each day for 6 weeks, and the AD group and Aqp4-/--AD group were injected with D-galactose by intraperitoneal each day for 6 weeks. MRI tracer Gd-DTPA (10 mmol/L, 2 μL) was injected into the hippocampus of the rats. MRI scan was performed at the end of 0.5 h, 1.5 h, 1 h, 2 h, and 3 h to observe the dynamic distribution of the Gd-DTPA in the hippocampus and the diffusion rate D*, clearance rate k' and half-life t1/2 measured.@*RESULTS@#The diffusion rate D* in Sham group was (2.66±0.36)×10-6 mm2/s, the diffusion rate D* in AD group was (2.72±0.62)×10-6 mm2/s, the diffusion rate D* in Aqp4-/--Sham group was (2.75±0.47)×10-6 mm2/s, the diffusion rate D* in Aqp4-/--AD group was (2.802±0.55)×10-6 mm2/s, and there was no statistically significant difference in the four groups (One-Way ANOVA, P>0.05).The clearance rate k' in Sham group was (4.57±0.14)×10-4/s, the clearance rate k' in AD group was (3.68±0.22)×10-4/s, the clearance rate k' in Aqp4-/--Sham group was (3.17±0.16)×10-4/s, the clearance rate k' in Aqp4-/--AD group was (2.59±0.19)×10-4/s, and there was significant difference in the four groups (One-Way ANOVA, P<0.05). The half-life t1/2 in Sham group was (0.67±0.12) h, the half-life t1/2 in AD group was (0.88±0.08) h, the half-life t1/2 in Aqp4-/--Sham group was (1.12±0.15) h, the half-life t1/2 in Aqp4-/--AD group was (1.58±0.11) h, and there was significance difference in the four groups(one-way ANOVA,P<0.05).@*CONCLUSION@#The ISF drainage is slow after AD and the loss of Aqp4 in the AD makes the ISF drainage obviously slow down, Aqp4 plays an important role in AD to remove the metabolism of waste out of the brain.

Advances on Genetic Research of Ossification of the Posterior Longitudinal Ligament / 中国微创外科杂志

[Summary] The ossification of the posterior longitudinal ligament ( OPLL ) is caused by environmental , genetic and other factors.With the development of genomics research , researchers have found that mutations are important factors inducing OPLL . Despite the genomics research on OPLL has made important advances , no highly correlation has been found between OPLL and the exact single nucleotide polymorphisms (SNPs) loci.The pathogenesis of OPLL needs further exploration .

Expression and activity analysis of Enterovirus 71 3C protease in Escherichia coli / 病毒学报

The recombinant plasmid carrying the gene encoding 3C protease of Enterovirus 71 (EV71) was constructed, the recombinant protein was then expressed and purified, the functional activity was also measured. Firstly, the 3C protease gene was inserted into pET28a vector, the constructed recombinant plasmid was transformed into E. coli BL21 (DE3) for expression under the induction of IPTG. The expressed protein was purified by affinity chromatography (Ni-NTA) and the N-terminus His-tag was cleaved by enterokinase from 3C protease. The activity of 3C protease was evaluated with fluorescent peptide substrates. It was verified by restriction analysis and sequencing that recombinant plasmid pET28a-3C was constructed correctly and functionally expressed in E. coli BL21 (DE3) resulting in the production of recombinant 3C protease with a size of 22kD. Both His-tag and non-His-tag (cleaved by enterokinase) 3C protease exhibited similar enzyme activity to 3B-3C fluorescent peptide with Km, Vmax and Kcat values of 22 microM, 434nM. Min(-1) and 0.0669 Min(-1), respectively. The optimial pH and temperature were 7.0 and 30-37 degrees C, respectively. The acquirement of recombinant purified 3C protease with high activity has paved the way of further studies on anti-viral inhibitors, structural protein assembly, vaccine development and detection methods of EV71.