Brain magnetic resonance imaging （MRI） of the elderly often reveals white matter changes （WMCs） with substantial variability across individuals. Our study was designed to explore MRI features and site-specific fac...Brain magnetic resonance imaging （MRI） of the elderly often reveals white matter changes （WMCs） with substantial variability across individuals. Our study was designed to explore MRI features and site-specific factors of ischemic WMCs. Clinical data of consecutive patients diagnosed with ischemic cerebral vascular disease who had undergone brain MRI were collected and analyzed. Multi-logistic regression analysis comparing patients with mild versus severe WMCs was performed to detect independent associations. Analyses of variance （ANOVAs） were used to detect regionally specific differences in lesions. We found that lesion distribution differed significantly across five cerebral areas, with lesions being predominant in the frontal lobe and parieto-occipital area. To explore WMCs risk factors, after adjusting for gender, diabetes mellitus, and hypertension, only age （P〈0.01）, creatinine （P=0.01）, alkaline phosphatase （ALP） （P=0.01） and low-density lipoprotein cholesterol （LDL-C） （P=0.03） were found to be independently associated with severe WMCs. Age （P〈0.001） was strongly associated with WMCs in the frontal lobe while hypertension was independently related to lesions in the basal ganglia （P=0.048） or infratentorial area （P=0.016）. In conclusion, MRI of WMCs showed that ischemic WMCs occurred mostly in the frontal lobe and parieto-occipital area. The infratentorial area was least affected by WMCs. Typically, age-related WMCs were observed in the frontal lobes, while hypertension-related WMCs tended to occur in the basal ganglia and infratentorial area.展开更多
In 1991, we found that methylation outside the PvuⅡ recognition sequence could partially inhibit its cleavage activity. To clarify the molecular mechanism, three plasmids with different methylation states were constr...In 1991, we found that methylation outside the PvuⅡ recognition sequence could partially inhibit its cleavage activity. To clarify the molecular mechanism, three plasmids with different methylation states were constructed. Then, together with the original one, four plasmids were digested with different amounts of PvuⅡ. Results show that methylation on both sites results in 90% inhibition; moving the methylated site one base further away decreases the inhibitory effect to about 30%; with the adjacent dam methylation site eliminated, the inhibitory effect disappears. The data suggest that the inhibition of cleavage activity caused by outside methylation is not "all or none", and the degree of inhibition is dependent on the position and the number of methylated bases.展开更多
基金This work was supported by grants from Scientific Research Project of Health and Family Planning of Hubei Province （No. WJ2015MB056）, Natural Science Foundation of Hubei Province （No. 2015CFB572）, and Clinical Research Physician Program of Tongji Medical College, HUST.
文摘Brain magnetic resonance imaging （MRI） of the elderly often reveals white matter changes （WMCs） with substantial variability across individuals. Our study was designed to explore MRI features and site-specific factors of ischemic WMCs. Clinical data of consecutive patients diagnosed with ischemic cerebral vascular disease who had undergone brain MRI were collected and analyzed. Multi-logistic regression analysis comparing patients with mild versus severe WMCs was performed to detect independent associations. Analyses of variance （ANOVAs） were used to detect regionally specific differences in lesions. We found that lesion distribution differed significantly across five cerebral areas, with lesions being predominant in the frontal lobe and parieto-occipital area. To explore WMCs risk factors, after adjusting for gender, diabetes mellitus, and hypertension, only age （P〈0.01）, creatinine （P=0.01）, alkaline phosphatase （ALP） （P=0.01） and low-density lipoprotein cholesterol （LDL-C） （P=0.03） were found to be independently associated with severe WMCs. Age （P〈0.001） was strongly associated with WMCs in the frontal lobe while hypertension was independently related to lesions in the basal ganglia （P=0.048） or infratentorial area （P=0.016）. In conclusion, MRI of WMCs showed that ischemic WMCs occurred mostly in the frontal lobe and parieto-occipital area. The infratentorial area was least affected by WMCs. Typically, age-related WMCs were observed in the frontal lobes, while hypertension-related WMCs tended to occur in the basal ganglia and infratentorial area.
文摘In 1991, we found that methylation outside the PvuⅡ recognition sequence could partially inhibit its cleavage activity. To clarify the molecular mechanism, three plasmids with different methylation states were constructed. Then, together with the original one, four plasmids were digested with different amounts of PvuⅡ. Results show that methylation on both sites results in 90% inhibition; moving the methylated site one base further away decreases the inhibitory effect to about 30%; with the adjacent dam methylation site eliminated, the inhibitory effect disappears. The data suggest that the inhibition of cleavage activity caused by outside methylation is not "all or none", and the degree of inhibition is dependent on the position and the number of methylated bases.
