Improved method for the quality assurance of [C-11]choline.

[C-11]choline is a very promising radiomarker for the diagnosis of various human tumors using Positron Emission Tomography (PET). The existing quality control process for [C-11]choline is complicated and combines two HPLC methods with limited separation and sensitivity which prevent the accurate determination of the specific activity. We have developed a new efficient single HPLC method for the detection of choline chloride and dimethylaminoethanol with high resolution and sensitivity using cation-exchange chromatography.

Survival of enteric bacteria in seawater.

Enteric bacteria exposed to the marine environment simultaneously encounter a variety of abiotic and biotic challenges. Among the former, light appears to be critical in affecting seawater survival; previous growth history plays a major part in preadaptation of the cells, and stationary phase cells are generally more resistant than exponentially growing ones. Predation, mostly by protozoa, is probably the most significant biotic factor. Using Escherichia coli as a model, a surprisingly small number of genes was found that, when mutated, significantly affect seawater sensitivity of this bacterium. Most prominent among those is rpoS, which was also dominant among genes induced upon transfer to seawater.

Potential (18)F-labeled biomarkers for epidermal growth factor receptor tyrosine kinase.

As PET candidate tracers for EGFr-TK, five 4-(anilino)quinazoline derivatives, each fluorinated in the aniline moiety, were prepared. Each was tested in vitro for inhibition of EGFr autophosphorylation in A431 cell line. The leading compounds were then radiolabeled with (18)F and cell binding experiments, biodistribution and PET studies in A431 tumor-bearing mice were performed. Metabolic studies were carried out in a mice control group. From our results, we concluded that while in vitro experiments indicates efficacy of 4-(anilino)quinazoline compounds, kinetic factors and rapid blood clearance make them unsuitable as tracers for nuclear medicine imaging of EGFr-TK.

Seawater Activation of Escherichia coli Gene Promoter Elements: Dominance of rpoS Control.

The release of non-disinfected wastewater into the marine environment is a common practice in many countries; nevertheless, the molecular mechanisms involved in determining the survival of enteric bacteria in seawater are poorly understood, in spite of the obvious public health implications. In a methodological attempt to address this issue, a plasmid-based collection of 687 Escherichia coli distinct promoter::luxCDABE fusions was screened to identify promoters that are induced upon exposure to seawater. The luminescence driven by 22 out of these promoters reproducibly increased at least two-fold in an artificial seawater medium; only 9 of the corresponding genes have previously been assigned a function. The most prominent characteristic of the induced genes was that most (18 out of 22) were under rpoS control. The induction of these seawater-responsive promoters was evaluated in different media to identify the cause of the increased transcription. Salinity or osmolarity was instrumental in only four cases, and in three promoters, increased pH also seemed to play a role; however, the most significant environmental effector in inducing the majority of the seawater-induced promoters appeared to be nutrient limitation.

Specific detection of p-chlorobenzoic acid by Escherichia coli bearing a plasmid-borne fcbA'::lux fusion.

In this communication we report on a genetically engineered bacterium that reacts by light emission to the presence of 4-chlorobenzoic acid. To construct this strain, DNA fragment (1.7 kb) upstream from the 4-chlorobenzoic acid dehalogenase (fcb) operon of Arthrobacter SU was fused to Vibriofischeri luxCDABE genes. An Escherichia coli strain transformed with a multi-copy plasmid (pASU) bearing this fusion responded to the presence of 4-chlorobenzoic acid and a few closely related compounds by increased luminescence, exhibiting a high specificity but a relatively low sensitivity. While it could be somewhat, improved by manipulating the experimental pH, sensitivity remained too low for real time applicability. Nevertheless, the principle of using dehalogenase promoters as environmental pollution sensor was demonstrated.