The use of a second reporter plasmid as an internal standard to normalize luciferase activity in transient transfection experiments may lead to a systematic error.

beta-galactosidase reporter plasmids containing different viral or minimal promoters are commonly used to correct variable transfection efficiencies in transient transfection experiments. The transcriptional activity of these promoters is thought to be stable under most circumstances. To determine if expression of beta-galactosidase from the commonly used beta-galactosidase plasmids remains stable upon stimulation of the cells with agonists we performed transient transfection experiments. CHO cells stably expressing the rat AT(1A) receptor were transfected with RSVbeta- or CMVbeta- or pTKbeta plasmids alone or together with a reporter construct in which luciferase transcription is driven by the c-fos promoter. Luciferase and/or beta-galactosidase activity was measured from the lysate of cells treated with angiotensin II or serum. We found that agonists increased the transcriptional activity of the different beta-galactosidase plasmids. The effect of angiotensin II and serum was different on the different promoters. Finally, cotransfection of other plasmids also modulated beta-galactosidase activity. These agonist induced variations of beta-galactosidase activity may influence the analysis and interpretation of the results in a systematic manner. Consequently we conclude that the use of a second reporter system to control for transfection efficiency in certain types of experiments may lead to a systematic error and is questionable as a general procedure.

Extracellular signal-regulated kinase and the small GTP-binding protein p21Rac1 are involved in the regulation of gene transcription by angiotensin II.

To study the role of extracellular-signal-regulated kinase (ERK) cascade and the small GTP-ase proteins in the activation of the c-fos promoter by angiotensin II (AII), transient transfection experiments were performed in CHO cells stably expressing the rat AT(1A) receptor. In this system AII activated ERK in 1 min and also increased the transcriptional activity of the c-fos promoter-luciferase reporter gene construct. The activation of the promoter proved to be dependent on the Ras-Raf-ERK cascade as cotransfection of expression vectors known to specifically inhibit this cascade blocked the effect of AII. Dominant-negative p21Rac1 mutant partially blocked the activation of the c-fos promoter by AII. However, activation of the c-fos promoter was independent of protein kinase C (PKC) as bisindolylmaleimide I, a specific PKC inhibitor did not block the effect of AII. These results suggest that AII activates the transcription of the c-fos through the Ras-Raf-ERK cascade. Furthermore, p21Rac1 is involved in the modulation of the c-fos promoter by AII.

Serological evidence of adenovirus infection in cats.

The widespread presence of adenoviruses in various species makes it probable that infection and the carrier state also exist in cats. On the basis of these considerations, investigations were carried out to find antibodies against adenovirus in sera from different cat populations kept under different conditions. For the antibody detection, purified adenovirus was used in an indirect ELISA. To produce positive serum, SPF cats were immunized with a purified hexon preparation. Altogether 632 field sera of different origin were tested. Among field samples, adenovirus seropositivity varied between 10-26%.

Molecular epidemiology of a cluster of cases due to Klebsiella pneumoniae producing SHV-5 extended-spectrum beta-lactamase in the premature intensive care unit of a Hungarian hospital.

Fifteen nosocomial cases of extended-spectrum beta-lactamase-producing Klebsiella pneumoniae occurred among 132 neonates in a premature intensive care unit in Hungary in June through November 1998. Fourteen strains were indistinguishable by molecular biological typing and harbored the same single conjugative extended-spectrum beta-lactamase-encoding plasmid that was spontaneously found in a Serratia marcescens strain in the same patient.

Induction of human cytomegalovirus (HCMV)-glycoprotein B (gB)-specific neutralizing antibody and phosphoprotein 65 (pp65)-specific cytotoxic T lymphocyte responses by naked DNA immunization.

Plasmids expressing the human cytomegalovirus (HCMV) glycoprotein B (gB) (UL55) or phosphoprotein 65 (pp65) (UL83) were constructed and evaluated for their ability to induce immune responses in mice. The full-length gB as well as a truncated form expressing amino acids 1-680 of gB, and lacking the fragment encoding amino acids 681 907 including the transmembrane domain of gB (gB680) were evaluated. Immunization of mice with plasmids coding for gB or gB680 induced ELISA and neutralizing antibodies, with the highest titres in mice immunized with the gB680 plasmid. Mice immunized with the gB plasmid predominantly produced IgG2a gB-specific antibody, while the gB680 plasmid raised mostly IgG1 anti-gB antibody. Mice immunized with the pp65 plasmid developed pp65-specific cytotoxic T lymphocytes (CTL) and ELISA antibodies. Immunization with a mixture of both gB and pp65 plasmids raised antibodies to both proteins and pp65-specific CTL, indicating a lack of interference between these two plasmids. These results suggest that DNA immunization is a useful approach for vaccination against HCMV disease.

Taguchi optimisation of ELISA procedures.

We propose a new method in the field of ELISA optimization using an experimental design called the Taguchi method. This can be used to compare the net effects of different conditions which can be both qualitative and quantitative in nature. The method reduces the effects of the interactions of the optimized variables making it possible to access the optimum conditions even in cases where there are large interactions between the variables of the assay. Furthermore, the proposed special assignment of factors makes it possible to calculate the biochemical parameters of the ELISA procedure carried out under optimum conditions. Thus, the calibration curve, the sensitivity of the optimum assay, the intra-assay and inter-assay variability can be estimated. The method is fast, accessing the results in one step, compared to the traditional, time-consuming 'one-step-at-a-time' method. We exemplify the procedure with a method to optimize the detection of ScFv (single chain fragment of variable) phages by ELISA. All the necessary calculations can be carried out by a spreadsheet program without any special statistical knowledge.

Fast method to remove UV absorbing agarose gel contamination from DNA samples.

Agarose gel electrophoresis and subsequent purification of DNA bands from the agarose gel is a widely used molecular biological method. There are different methods to achieve this goal, however they have different advantages and disadvantages. One major problem is the presence of different contaminants in the final sample. We developed a method which is effective in removal of the agarose contaminants.