A method of estimating lag between brain areas based on windowed harmonic wavelet transform / 生物医学工程学杂志

Aiming at local field potential, the present paper introduces a method of estimating lag of neuron activities between brain areas based on windowed Harmonic wavelet transform (WHWT). Firstly, the WHWT of signals of two brain areas are calculated. Secondly, the instantaneous amplitude of the signals is calculated and finally, these amplitudes are cross-correlated and the lag at which the cross-correlation peak occurs is determined as the lag of neurons activities. Comparing with amplitude cross-correlation based on Gabor wavelet transform (GWT) or Hilbert transform (HT), this method is more precise and efficient in estimating the directionality and lag.

Changes of local field potentials in M1 underlying the specific behavior in rat / 生物医学工程学杂志

The local field potentials (LFPs) underlying specific behavior were recorded and analyzed in this paper from primary motor cortex (M1) with several medium, such as the self-made single channel micro-electrodes, the system of multi-channels physiological signal acquisition and processing and so on. During the experiment, the specific behavior was divided into four periods according to the changes of the recorded LFPs and the changes of the specific behavior recorded simultaneously in rats. The four periods were named prophase of catching period, planning period, catching period and the completion period, respectively. Then several methods were used for the analysis of the LFPs by MATLAB, such as time domain analysis, power spectral distribution analysis and time-frequency analysis. The results suggested that the LFPs which were caused by different behavior from a large number of movement-related neurons of M1 during the specific behavior in the process of catching play an important part in the "code" guiding role in rats. The results demonstrat that the LFPs of M1 may provide a feasibility to discriminate the motor behavior of forelimb.

A telemetery system for neural signal acquiring and processing / 生物医学工程学杂志

Recording and extracting characteristic brain signals in freely moving animals is the basic and significant requirement in the study of brain-computer interface (BCI). To record animal's behaving and extract characteristic brain signals simultaneously could help understand the complex behavior of neural ensembles. Here, a system was established to record and analyse extracellular discharge in freely moving rats for the study of BCI. It comprised microelectrode and micro-driver assembly, analog front end (AFE), programmer system on chip (PSoC), wireless communication and the LabVIEW used as the platform for the graphic user interface.

"The""modification""Type Microsatellite Change in High Frequency Microsatellite Instability Colorectal Cancer Closely Relating to MLH1 and KRAS Mutation" / 现代生物医学进展

Microsatellite instability(MSI)was defined according to the frequency of positive findings in a panel of MSI markers.High frequency MSI(MSI-H)was the phenotype in which repeat sequences were extraordinarily unstable, and was considered to be the bona fide phenotype of DNA mismatch repair defection. However base substitutions in some well studied oncogenes or tumor suppressors were reported to be uncommon in MSI-H tumors. To explore this obvious contradiction, the relationship between MSI and KRAS gene mutations were studied in a panel of 76 human colorectal carcinomas, the whole exon of MLH1 and MSH2 were sequenced for MSI-H tumors. KRAS gene mutation was confirmed by similar frequencies in tumors of different MSI status. Intriguingly, all of the KRAS mutant MSI-H tumors harbored sequence alterations in MLH1gene, which was a key player in DNA mismatch repair system. This implied that in MSI-H tumors carrying MMR mutations, KRAS mutation were frequently and almost exclusively occurred. Furthermore, these MMR mutants were uniformly carrying a unique modification + jumping type MSI, which was different to MSI-H tumors without MLH1 or MSH2 gene mutations. This study shaded lights on the heterogeneity of MSI-H tumors, and implied the connection between modification type MSI and DNA mismatch defection.

Correlation between over expression of BUBR1 and chromosomal instability in colorectal carcinoma / 现代生物医学进展

Objective:Over expression of BUBR1 protein was reported in several human malignancies,however whether BUBR1 plays a role in chromosomal instability phenotype remains in controversy.This study was to explore the roll of BUBR1 protein in CIN phenotype in CRC.Methods:BUBR1 expression was studied immunohistochemieally in a panel of 93 advanced sporadic eolorectal cancers.Microsatellite status was evaluated by high resolution microsatellite analysis assay,TP53 gene mutation by direct sequencing and DNA ploidy by laser scanning cytometery.The relationship between BUBR1 overexpression and TP53 gene mutation,mierosatellite status,and DNA ploidy were studied.Results:BUBR1 overexpression was confirmed in 69% of cases.The overexpression was more frequent in tumor without high frequency microsatellite instability (P＜0.01) and TP53 mutation (P＜0.05).There was no statistic correlation between DNA aneuploidy and BUBR1 overexpression; however,a tendency that aneuploidy tumors had higher percentage of BUBR1 overexpression was shown.BUBR1 overexpression was not statistically related with clinieopathological factors.Conclusion:The linkage between BUBR1 overexpression and molecular factors indicating a CIN background implied that BUBR1 overexpression was indeed related with chromosomal instability in colorectal cancer.

"Modification" type microsatellite instability is correlated with p53 mutation in sporadic colorectal cancer / 肿瘤研究与临床

Objective High frequency microsatellite instability(MSI-H)was considered to be the phenotype of DNA mismatch repair(MMR)deficiency.However,a contradiction was noticed that p53 mutation is reposed to be extremely rare in MSI-H tumors.The aim of the current study was to confirm and try to explain this a phenomenon.We have demonstrated a direct link between MMR model and"modification"type MSI,and suggested the new categorization system of MSI by quantification of MSI profile.Based on this categorization system we studied the relationship between MSI and mutation of p53 oncogene in colorectal cancer.Methods A series of 180 sporadic colorectal cancer cases were investigated for their microsatellite status and p53 mutations.High resolution fluorescent microsatellite instability analysis assay and direct sequencing were employed in this study.Results Two definite patterns of microsatellite instability were confirmed,i.e."modification" type and "jumping" type MSI. In colorectal cancer,low frequency microsatellite instability (MSI-L)cases all showed pure"modification"type,while"jumping"type MSI changes were confirmed in all MSI-H cases.MSI-H was related with proximal tumor location and poorly differentiated.p53 mutation rate was more frequent in well differentiated tumors.Interestingly.MSI-L tumor showed a 40% mutation rate which is similar with MSS tumor 41%,however,in MSI-H tumors no p53 mutation was confirmed.Conclusions We confirm in human colorectal cancers,the"modification"type MSI might be connected with MMR defection.The mechanism underlying MSI-H phenotype was supposed to be other than MMR deficiency.