Evaluation of an 18F-labeled oligonucleotide probe targeting p21(WAF1) transcriptional changes in human tumor cells.

The ability to image gene expression using 18F-labeled antisense oligonucleotides (asODNs) directed to specific mRNA transcripts during, or immediately following, radio- or chemotherapy would be a valuable clinical tool to monitor the early tumor response to treatment. Imaging of upregulated p21 mRNA postirradiation using 18F-labeled asODNs could offer insights into early tumor responses by detecting signs of accelerated cellular senescence. Thus, the aim of this work was to evaluate the uptake and distribution of a (radio)-fluorinated asODN in vitro in HCT116 p21(+/+) human colon carcinoma cells, asODN and a random sequence oligonucleotide (rsODN) were conjugated with a (radio)fluorine prosthetic group. Irradiated HCT116 cells were treated with naked or liposome-transfected ODNs. Cell fractionation, confocal microscopy, immunofluorescence, and Western blot studies were performed to observe uptake, distribution, and antisense activity of the probes. [F]asODN demonstrated similar antisense binding ability as the unlabeled asODN to p21 mRNA. Liposomal-transfected 18F-labeled asODNs and rsODNs exhibited a three-to fivefold increase in uptake at 2.5 h compared to the naked [18F]ODNs. Distribution of transfected [18F]asODN in the cytoplasm and endosomes increased over time whereas no change in intracellular distribution was observed with transfected [18F]rsODN or naked ODNs. Antisense activity was not compromised with the addition of a fluorine moiety on asODN. The cellular accumulation and distribution of the (radio)fluorinated ODNs was not altered by the addition of the prosthetic group. Radiolabeled ODNs were able to penetrate the cell with preferential uptake observed with the liposome-transfected probes. Increased distribution of [18F]asODN in the cytoplasm suggests the probe is available for targeting its transcript mRNA. This warrants further investigations into the potential of [18F]asODN to image accelerated senescence postirradiation.

Evaluation of the stability of (99m)Tc-ECD and stabilized (99m)Tc-HMPAO stored in syringes.

OBJECTIVE: To determine and compare the stability of (99m)Tc-ECD and stabilized (99m)Tc-HMPAO when stored in syringes over an 8-h period. METHODS: (99m)Tc-ECD and stabilized (99m)Tc-HMPAO were prepared according to the manufacturers' protocols, with the following exception: eluate less than 60 min old was used to prepare (99m)Tc-HMPAO rather than the recommended 30 min. Once prepared, 185 MBq (5 mCi) of both products were drawn into 5-mL syringes and allowed to sit at room temperature. At 2, 4, 6, and 8 h after preparation, the radiochemical purity (RCP) of the contents of the syringes was determined and compared to the RCP of the products in vials. Retention of activity of each product in syringes was also evaluated by measuring activity remaining in each syringe (and filter, in the case of (99m)Tc-HMPAO) after expressing its contents. RESULTS: The RCP of stabilized (99m)Tc-HMPAO stored in syringes decreased from a mean of 87.7% at 2 h to 74.0% at 8 h after preparation. In contrast, (99m)Tc-ECD retained an RCP of greater than 94% throughout the time tested. The impurity that appeared to increase over time with (99m)Tc-HMPAO was found to be sodium pertechnetate. Total retention of activity remaining in the syringe and filter ranged from 11.6% at 2 h to 9.5% at 8 h for (99m)Tc-HMPAO; the syringe itself retained less than 5% of the total activity at all time periods. (99m)Tc-ECD exhibited 6.2% to 11.3% retention of activity in the syringe. The sorption of sodium pertechnetate to the syringe for the same time period was less than 1%. CONCLUSIONS: (99m)Tc-ECD is a more stable product than stabilized (99m)Tc-HMPAO in a syringe. Both products demonstrate retention of radioactivity in the syringe. Some of this retention may denote sorption of the products to plastic.

Pharmaceutical interference with the [14C] carbon urea breath test for the detection of Helicobacter pylori infection.

Helicobacter pylori bacteria reside in the mucosal lining of the stomach where, due to a variety of factors, the infection predisposes patients to peptic ulcer disease. Detection of H. pylori is important in the treatment and follow-up of patients with peptic ulcer disease and the urea breath test is the method of choice. This article will briefly review the methods for diagnosing H. pylori, emphasizing the [(14)C]urea breath test. The agents which can interfere with the results of the breath test will be reviewed and the role of the consulting pharmacist will be discussed.

Measurement of gastric emptying during and between meal intake in free-feeding Lewis rats.

A new scintigraphic measurement technique is described that allows accurate assessment of gastric emptying in between as well as during a number of successive meals. Measurements were made every minute of food intake, gastric nutrient filling, and gastric emptying over a 6 h, 40 min period in conscious, free-feeding, loosely restrained rats. Before receiving access to the food, the animals had been deprived for a period of 31 h. Over the full duration of the experiment, an average rate of gastric emptying of 2.46 +/- 0.18 (SE) kcal/h was established. During most meals, however, the gastric emptying rate was increased so that an average of 26.9 +/- 2.7% of the ingested calories was emptied while the animals were feeding, with an average emptying rate of 0.15 +/- 0.014 kcal/min or 8.88 +/- 0.84 kcal/h. This transient increase in the rate of gastric emptying was followed by a subsequent slowing of gastric emptying after meal termination; in the 10-min postmeal interval, an average emptying rate of 0.96 +/- 0.12 kcal/h was found. Despite these fluctuations during and immediately after meals, a relatively constant rate of caloric emptying is maintained over longer periods. There were no differences between the emptying rate during the first meal when the gastrointestinal tract was still empty, compared with later meals when the gastrointestinal tract had been filled with food. The emptying rate during the 10-min postmeal interval, however, was significantly reduced during later meals. The results suggest that gastric emptying is controlled by different mechanisms during and after the ingestion of food and that these mechanisms remain in effect at various degrees of gastrointestinal filling.