Expression of c-Fos in rats organs after electrical injury / 法医学杂志

OBJECTIVE@#To study the expression of c-fos in organs after rats electrified.@*METHODS@#The brain, lung, heart, liver, spleen, kidney, muscle of electrified limb, and cutis of electrified limb of all experimental rats and those organs of control groups were dissected to detect the expression of c-fos by using immunohistochemistry staining, and the staining intensity were assessed by image analysis system.@*RESULTS@#The expression of c-fos was observed in brain, heart, liver, lung, kidney and muscle in electrified directly group, the amount of expression reached peak at 2 h after electrified and decreasing at 8 h after electrified, and the expression showed faintness in electrified at the immediate after death group. The expressions of c-fos in spleen and cutis is negative in all groups. The expression of c-fos in all detected organs was negative in other rats that were electrified after death.@*CONCLUSION@#c-fos can be regard as a target in identifying electrical injury, whether it formed at antemortem or postmortem.

Co-expressions of phosphoenolpyruvate synthetase A (ppsA) and transketolase A (tktA) genes of Escherichia coli / 生物工程学报

Metabolic engineering is the analysis of metabolic pathway and designing rational genetic modification to optimize cellular properties by using principle of molecular biology. Aromatic metabolites such as tryptophan, phenylalanine, and tyrosine are essential amino acids for human and animals. In addition, phenylalanine is used in aspartame production. Escherichia coli and many other microoganism synthesize aromatic amino acids through the condensation reaction between phospho-enolpyruvate (PEP) and erythrose-4-phosphate(E4P) to form 3-deoxy-D-arabinoheptulosonate 7-phosphate(DAHP). But many enzymes compete for intracellular PEP, especially the phosphotransferase system which is responsible for glucose transport in E. coli. This system uses PEP as a phosphate donor and converts it to pyruvate, which is less likely to recycle back to PEP. To channel more carbon flux into the aromatic pathway, one has to overcome pathways competing for PEP. ppsA and tktA are the key genes in central metabolism of aromatic amino acids biosynthesis. ppsA encoding phosphoenolpyrucate synthetase A (PpsA) which catalyzes pyruvate into PEP; tktA encoding transketolase A which plays a major role in erythrose-4-phosphate (E4P) production of pentose pathway. We amplified ppsA and tktA from E. coli K-12 by PCR and constructed recombinant plasmids of them in pBV220 vector containing P(R)P(L) promoter. Because of each gene carrying P(L) promoter, four productions of ligation were obtained. The monoclonal host containing recombinant plasmids was routinely grown in Luria-Bertani (LB) medium added Ampicillin at 37 degrees C overnight, and then inoculated in LB (Apr) medium by 3%-5% in flasks on a rotary shaker at 30 degres C, induced at 42 degrees C for 4.5 hours when OD600 = 0.4, cells were obtained by centrifugation at 10,000 r/min at 4 degrees C. The results of SDS-PAGE demonstrated that the bands at 84kD and 73kD were more intensive than the same ones of the controls. The specific activity of PpsA in crude extracts was increased by 10.8-fold, and TktA, by 3.9-fold. When both genes were co-expressed in E. coli, the activity of PpsA varied from 2.1-9.1 fold comparing to control, but the activity of TktA was relatively stable(3.9-4.5 fold). Whatever the two genes were expressed respectively or cooperatively, both could promote the production of DAHP, the first intermediate of the common aromatic pathway, but co-expression was more effective on forming DAHP. The results demonstrate that co-expression of ppsA and tktA can improve the production of DAHP to near theoretical yield. This report details a different strategy based on co-expression of two genes in one vector in vivo to release the burden and paves the way for construction of genetic engineering bacteria for further research.