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Initially acquired memory dissipates rapidly if not consolidated. Such memory decay is thought to result either from the inherently labile nature of newly acquired memories or from interference by subsequently attained information. Here we report that a small G protein Rac-dependent forgetting mechanism contributes to both passive memory decay and interference-induced forgetting in Drosophila. Inhibition of Rac activity leads to slower decay of early memory, extending it from a few hours to more than one day, and to blockade of interference-induced forgetting. Conversely, elevated Rac activity in mushroom body neurons accelerates memory decay. This forgetting mechanism does not affect memory acquisition and is independent of Rutabaga adenylyl cyclase-mediated memory formation mechanisms. Endogenous Rac activation is evoked on different time scales during gradual memory loss in passive decay and during acute memory removal in reversal learning. We suggest that Rac's role in actin cytoskeleton remodeling may contribute to memory erasure., (2010 Elsevier Inc. All rights reserved.)

Objective: To establish the methods for isolation, purification and function identification of Syrian golden hamster islets., Methods: The Langerhans islets were isolated and purified from golden hamster pancreas by intra-ductal collagenase V perfusion and discontinuous Ficoll density gradient centrifugation. After isolation, the islet yield and purity were evaluated with DTZ staining. The islet function was assessed using glucose-stimulated insulin secretion test., Results: The total number of purified islets from one donor hamster was 359-/+35 islet equivalent (IEQ), with the purity and viability of the isolated islets of more than 90%. In response to glucose stimulations at 5.8 and 16.7 mmol/L, the secretion of insulin by the islets was 3.29-/+0.3 and 11.12-/+0.57 mU/L, respectively, showing a 2.28-fold higher insulin release by high-concentration than by low- concentration glucose stimulation (P<0.01)., Conclusion: The methods of collagenase V digestion and gradient centrifugation result in high yield and high purity of the isolated hamster islets.

Objective: To test the hypothesis that the introduction of antisense transforming growth factor beta receptor I (TBRI) plasmid and antisense tissue inhibitor of matrix metalloproteinase (TIMP-1) eukaryotic expressing plasmid into a rat liver fibrosis model may influence the progression of liver fibrosis., Methods: Fragments of TBRI cDNA and TIMP-1 cDNA were obtained by reverse transcription polymerase chain reaction (RT-PCR) and then amplified by nest PCR. pcDNA3.1(+)-antisense TBRI eukaryotic expressing plasmid was constructed by directional and inverted joins with the purified linear pcDNA3.1(+) and the purified fragment of TBRI, as well as, pcDNA3.1(+)-antisense TIMP-1 eukaryotic expressing plasmid. The recombinant was identified by restriction endonuclease digestion and DNA sequence analysis. The recombinant plasmids were encapsulated with Lipofectmine 2000, and then they were injected intraperitoneally into the liver fibrosis model rats. The protein expression of type I collagen was evaluated by immunohistochemistry. VG staining of liver slides of the rats was used for histopathological examination., Results: Compared with the empty plasmid control group and the disease control group, the deposition of type I collagen decreased in the three antisense treatment groups: antisense TBRI group (4.37+/-1.30) x 10(5), P less than 0.05; antisense TIMP-1 group (3.40+/-0.91) x 10(5), probability value less than 0.05; antisense TBRI + antisense TIMP-1 group (0.90+/-0.32) x 10(5), P less than 0.01; treatment control group (6.90+/-1.61) x 10(5); disease control group (7.34+/-1.68) x 10(5); and the normal control group (0.41+/-0.21) x 10(5)]. Significant differences in the pathological grades of fibrosis were found between the normal control group and the other five groups (P less than 0.05) and also between the disease control group and the three antisense treatment groups (antisense TBRI group P less than 0.05; antisense TIMP-1 group P less than 0.05; antisense TBRI + antisense TIMP-1 group P less than 0.01), but no difference was found between the empty plasmid control group and disease control group (P more than 0.05)., Conclusion: Both antisense TBRI eukaryotic expressing plasmid and antisense TIMP-1 eukaryotic expressing plasmid can inhibit the progress of liver fibrosis. A combined action can inhibit the progress of liver fibrosis more.