The effects of irradiation on major histocompatibility complex expression and lymphocytic infiltration in the normal rat brain and the 9L gliosarcoma brain tumor model

The effects of irradiation on major histocompatibility complex (MHC) expression and lymphocytic infiltration in the normal rat brain and the 9L gliosarcoma brain tumor model were examined. Doses of irradiation administered were biologically equivalent to that used in the treatment of patients with malignant gliomas. No significant change in immune parameters was observed following irradiation in the normal rat brain. In the 9L gliosarcoma model irradiation did not suppress MHC expression or lymphocytic infiltration. These findings suggest that prior exposure to therapeutic irradiation need not adversely affect subsequent immunotherapies, and provide a foundation for future studies of immunomodulation in the irradiated brain.

Eukaryotic promoters drive gene expression in Escherichia coli

Eight eukaryotic promoters have been tested for their activity in vivo in Escherichia coli. The rat beta-actin, rat amylase, rat chymotrypsin B, mouse metallothionein I, rat insulin I, human insulin, Rous sarcoma virus long terminal repeat (RSV LTR) and hepatitis B viral precore promoter activities were measured by using the bacterial chloramphenicol acetyltransferase coding sequences as the reporter function and by primer extension RNA analysis. All eight promoter-chloramphenicol acetyltransferase constructs produce chloramphenicol acetyltransferase activity with the following relative strengths: RSV LTR greater than rat beta-actin greater than rat insulin I greater than rat amylase greater than hepatitis B virus precore greater than human insulin greater than rat chymotrypsin B greater than mouse metallothionein I. A primer extension analysis indicates that transcription from the RSV LTR, rat insulin I, and rat beta-actin promoters initiates at the sites expected for eukaryotic rather than prokaryotic promoters. Thus the site of initiation is determined by the DNA sequence rather than by the RNA polymerase.