Design, synthesis and biological evaluation of negatively charged ¹¹¹In-DTPA-octreotide derivatives.

Our previous studies indicated that (111)In-diethylenetriaminepentaacetic acid ((111)In-DTPA)-octreotide derivatives with an additional negative charge by replacing N-terminal d-phenylalanine (d-Phe) with an acidic amino acid such as l-aspartic acid (Asp) or its derivative exhibited low renal radioactivity levels when compared with (111)In-DTPA-D-Phe(1)-octreotide. On the basis of the findings, we designed, synthesized and evaluated two Asp-modified (111)In-DTPA-conjugated octreotide derivatives, (111)In-DTPA-Asp(1)-octreotide and (111)In-DTPA-Asp(0)-D-Phe(1)-octreotide. While (111)In-DTPA-Asp(1)-octreotide showed negligible AR42J cell uptake, (111)In-DTPA-Asp(0)-D-Phe(1)-octreotide exhibited AR42J cell uptake similar to that of (111)In-DTPA-D-Phe(1)-octreotide. When administered to AR42J tumor-bearing mice, (111)In-DTPA-Asp(0)-D-Phe(1)-octreotide exhibited renal radioactivity levels significantly lower than did (111)In-DTPA-D-Phe(1)-octreotide at 1 and 3 h post-injection. No significant differences were observed in tumor accumulation between (111)In-DTPA-Asp(0)-D-Phe(1)-octreotide and (111)In-DTPA-D-Phe(1)-octreotide after 1 and 3h injection. The findings in this study suggested that an interposition of an Asp at an appropriate position in (111)In-DTPA-D-Phe(1)-octreotide would constitute a useful strategy to develop (111)In-DTPA-D-Phe(1)-octreotide derivatives of low renal radioactivity levels while preserving tumor accumulation.

Preclinical investigation of potential use of thymidine phosphorylase-targeting tracer for diagnosis of nonalcoholic steatohepatitis.

INTRODUCTION: Although liver biopsy is the gold standard for the diagnosis of nonalcoholic steatohepatitis (NASH), it has several problems including high invasiveness and sampling errors. Therefore, the development of alternative methods to overcome these disadvantages is strongly required. In this study, we evaluated the potential use of our tracer targeting thymidine phosphorylase (TYMP), 5-[123I]iodo-6-[(2-iminoimidazolidinyl)methyl]uracil ([123I]IIMU) for the diagnosis of NASH. METHODS: The mice used as the NASH model (hereafter, NASH mice) were prepared by feeding a methionine- and choline-deficient diet for 4 weeks. A control group was similarly given a control diet. The expression levels of the TYMP gene and protein in the liver were examined by real-time reverse-transcription polymerase chain reaction and western blot analyses. The localizations of [125I]IIMU and the TYMP protein in the liver were examined by autoradiography and immunohistochemical staining, respectively. Finally, the mice were injected with [123I]IIMU and single-photon emission tomography (SPECT) imaging was conducted. RESULTS: The hepatic expression levels of TYMP were significantly lower in the NASH mice than in the control mice at both mRNA and protein levels, suggesting that a decrease in TYMP level could be an indicator of NASH. [125I]IIMU was uniformly distributed in the liver of the control mice, whereas it showed a patchy distribution in that of the NASH mice. The localization of [125I]IIMU was visually consistent with that of the TYMP protein in the liver of the control and NASH mice. SPECT analysis indicated that the hepatic accumulation of [123I]IIMU in the NASH mice was significantly lower than that in the control mice [SUV (g/ml): 4.14 ± 0.87 (Control) vs 2.31 ± 0.29 (NASH)]. CONCLUSIONS: [123I]IIMU may provide a noninvasive means for imaging TYMP expression in the liver and may be applicable to the diagnosis of NASH.

Improvement of an efficient separation method for chemicals in diesel exhaust particles: analysis for nitrophenols.

GOAL, SCOPE, AND BACKGROUND: Diesel exhaust is believed to consist of thousands of organic constituents and is a major cause of urban pollution. We recently reported that a systematic separation procedure involving successive solvent extractions, followed by repeated column chromatography, resulted in the isolation of vasodilatory active nitrophenols. These findings indicated that the estimation of the amount of nitrophenols in the environment is important to evaluate their effect on human health. The isolation procedure, however, involved successive solvent extractions followed by tedious, repeated chromatography, resulting in poor fractionation and in a significant loss of accuracy and reliability. Therefore, it was crucial to develop an alternative, efficient, and reliable analytical method. Here, we describe a facile and efficient acid-base extraction procedure for the analysis of nitrophenols. MATERIALS AND METHODS: Diesel exhaust particles (DEP) were collected from the exhaust of a 4JB1-type engine (ISUZU Automobile Co., Tokyo, Japan). Gas chromatography-mass spectrometry (GC-MS) analysis was performed with a GCMS-QP2010 instrument (Shimadzu, Kyoto, Japan). RESULTS: A solution of DEP in 1-butanol was extracted with aqueous NaOH to afford a nitrophenol-rich oily extract. The resulting oil was methylated with trimethylsilyldiazomethane and subsequently subjected to GC-MS analysis, revealing that 4-nitrophenol, 3-methyl-4-nitrophenol, 2-methyl-4-nitrophenol, and 4-nitro-3-phenylphenol were present in significantly higher concentrations than those reported previously. DISCUSSION: Simple acid-base extraction followed by the direct analysis of the resulting extract by GC-MS gave only broad peaks of nitrophenols with a poor detection limit, while the GC-MS analysis of the sample pretreated with (trimethylsilyl)diazomethane gave satisfactorily clear chromatograms with sharp peaks and with a significantly lowered detection limit (0.5 ng/ml, approximately 100 times). CONCLUSION: The present method involving an acid-base extraction, in situ derivatization, and GC-MS analysis has shown to be a simple, efficient, and reliable method for the isolation and identification of the chemical substances in DEP.

N-methyl-d-aspartate receptor dysfunction in the prefrontal cortex of stroke-prone spontaneously hypertensive rat/Ezo as a rat model of attention deficit/hyperactivity disorder.

AIM: We previously reported that stroke-prone spontaneously hypertensive rat/Ezo (SHRSP/Ezo) has high validity as an attention deficit/hyperactivity disorder (AD/HD) animal model, based on its behavioral phenotypes, such as inattention, hyperactivity, and impulsivity. Fronto-cortical dysfunction is implicated in the pathogenesis of AD/HD. In this study, we investigated prefrontal cortex (PFC) function in SHRSP/Ezo rats by electrophysiological methods and radioreceptor assay. METHODS: We recorded excitatory postsynaptic potential in layer V pyramidal neurons in the PFC by intracellular recording method to assess synaptic plasticity in the form of long-term potentiation (LTP). We also performed N-methyl-d-aspartate acid (NMDA) receptor binding assay in the PFC and hippocampus using radiolabeled NMDA receptor antagonist [3 H]MK-801. RESULTS: Theta-burst stimulation induced LTP in the PFC of genetic control, WKY/Ezo, whereas failed to induce LTP in that of SHRSP/Ezo. The Kd value of [3 H]MK-801 binding for NMDA receptors in the PFC of SHRSP/Ezo was higher than in the WKY/Ezo. Neither the Bmax nor Kd of [3 H]MK-801 binding in the SHRSP/Ezo hippocampus was significantly different to WKY/Ezo. CONCLUSION: These results suggest that the AD/HD animal model SHRSP/Ezo has NMDA receptor dysfunction in the PFC.

A novel and efficient synthesis of [2-11C]5-fluorouracil for prognosis of cancer chemotherapy.

PURPOSE: In order to facilitate the use of the PET-based Strauss test for 5-FU sensitivity, a rapid and facile synthesis of [2-11C]5-fluorouracil ([2-11C]5-FU), based on = [11C]phosgene ([11C]COCl2), is reported. METHOD: The key intermediate (E)-beta- benzoylamino-Alpha-fluoroacrylamide (1) and [11C]phosgene was submitted to cyclocondensation to give [2-11C]5-fluorouracil. RESULTS: [2-11C]5-Fluorouracil was synthesized in 17 min with high (25%) radiochemical yield. CONCLUSION: The present study provides a rapid, simple, and efficient synthesis of [2-11C]5-FU, that would serve as a useful prognostic PET tracer for 5-FU chemotherapy.

Redesign of negatively charged 111In-DTPA-octreotide derivative to reduce renal radioactivity.

INTRODUCTION: Radiolabeled octreotide derivatives have been studied as diagnostic and therapeutic agents for somatostatin receptor-positive tumors. To prevent unnecessary radiation exposure during their clinical application, the present study aimed to develop radiolabeled peptides which could reduce radioactivity levels in the kidney at both early and late post-injection time points by introducing a negative charge with an acidic amino acid such as L-aspartic acid (Asp) at a suitable position in 111In-DTPA-conjugated octreotide derivatives. METHODS: Biodistribution of the radioactivity was evaluated in normal mice after administration of a novel radiolabeled peptide by a counting method. The radiolabeled species remaining in the kidney were identified by comparing their HPLC data with those obtained by alternative synthesis. RESULTS: The designed and synthesized radiolabeled peptide 111In-DTPA-d-Phe-1-Asp0-d-Phe1-octreotide exhibited significantly lower renal radioactivity levels than those of the known 111In-DTPA-d-Phe1-octreotide at 3 and 24h post-injection. The radiolabeled species in the kidney at 24h after the injection of new octreotide derivative represented 111In-DTPA-d-Phe-OH and 111In-DTPA-d-Phe-Asp-OH as the metabolites. Their radiometabolites and intact 111In-DTPA-conjugated octreotide derivative were observed in urine within 24h post-injection. CONCLUSION: The present study provided a new example of an 111In-DTPA-conjugated octreotide derivative having the characteristics of both reduced renal uptake and shortened residence time of radioactivity in the kidney. It is considered that this kinetic control was achieved by introducing a negative charge on the octreotide derivative thereby suppressing the reabsorption in the renal tubules and affording the radiometabolites with appropriate lipophilicity.

111In-DTPA-d-Phe-1-Asp0-d-Phe1-octreotide exhibits higher tumor accumulation and lower renal radioactivity than 111In-DTPA-d-Phe1-octreotide.

INTRODUCTION: 111In-DTPA-d-Phe1-octreotide scintigraphy is an important method of detecting neuroendocrine tumors. We previously reported that a new derivative of 111In-DTPA-d-Phe1-octreotide, 111In-DTPA-d-Phe-1-Asp0-d-Phe1-octreotide, accomplished the reduction of prolonged renal accumulation of radioactivity. The aim of this study was to evaluate the tumor accumulation of 111In-DTPA-d-Phe-1-Asp0-d-Phe1-octreotide in vitro and in vivo by comparing it with 111In-DTPA-d-Phe1-octreotide. METHODS: The tumor accumulation of this octreotide derivative was determined by measuring its uptake using cultured AR42J cells in vitro and biodistribution studies in vivo. The distribution of the radiotracer and the extent of somatostatin receptor-specific uptake in the tumor were estimated by a counting method using AR42J tumor-bearing mice. The radioactive metabolite species in the tumor and kidney were identified by HPLC analyses at 3 and 24h post-injection of the 111In-DTPA-conjugated peptide. RESULTS: In both cases, in vitro and in vivo, the tumor radioactivity levels of 111In-DTPA-d-Phe-1-Asp0-d-Phe1-octreotide were approximately 2-4 times higher than those of 111In-DTPA-d-Phe1-octreotide. On in vitro cellular uptake inhibition and radioreceptor assay, 111In-DTPA-d-Phe-1-Asp0-d-Phe1-octreotide exhibited a binding affinity to somatostatin receptor highly similar to that of 111In-DTPA-d-Phe1-octreotide. As the additional cellular uptake of 111In-DTPA-d-Phe-1-Asp0-d-Phe1-octreotide was significantly lower at low temperature than at 37°C, it was considered that a cellular uptake pathway is involved in energy-dependent endocytotic processes. In the radiometabolite analysis of 111In-DTPA-d-Phe-1-Asp0-d-Phe1-octreotide, 111In-DTPA-d-Phe-Asp-OH was a major metabolite in the tumor at 24h post-injection. CONCLUSION: 111In-DTPA-d-Phe-1-Asp0-d-Phe1-octreotide exhibited higher tumor accumulation and persistence of tumor radioactivity than 111In-DTPA-d-Phe1-octreotide. We reasoned that this higher tumor accumulation would not be based on the receptor affinity but on a receptor-mediated endocytotic process involved in temperature-dependent cellular uptake. The present study demonstrated the great potential of the pharmaceutical development of a new radiolabeled peptide with high tumor accumulation and low renal radioactivity by the chemical modification of 111In-DTPA-d-Phe1-octreotide.

Synthesis and evaluation of radioiodinated cyclooxygenase-2 inhibitors as potential SPECT tracers for cyclooxygenase-2 expression.

UNLABELLED: Although several COX-2 inhibitors have recently been radiolabeled, their potential for imaging COX-2 expression remains unclear. In particular, the sulfonamide moiety of COX-2 inhibitors may cause slow blood clearance of the radiotracer, due to its affinity for carbonic anhydrase (CA) in erythrocytes. Thus, we designed a methyl sulfone-type analogue, 5-(4-iodophenyl)-1-[4-(methylsulfonyl)phenyl]-3-trifluoromethyl-1H-pyrazole (IMTP). In this study, the potential of radioiodinated IMTP was assessed in comparison with a (125)I-labeled celecoxib analogue with a sulfonamide moiety ((125)I-IATP). METHODS: The COX inhibitory potency was assessed by measuring COX-catalyzed oxidation by hydrogen peroxide. The biodistribution of (125)I-IMTP and (125)I-IATP was determined by the ex vivo tissue counting method in rats. Distribution of the labeled compounds to rat blood cells was measured. RESULTS: The COX-2 inhibitory potency of IMTP (IC(50) = 5.16 microM) and IATP (IC(50) = 8.20 microM) was higher than that of meloxicam (IC(50) = 29.0 microM) and comparable to that of SC-58125 (IC(50) = 1.36 microM). The IC(50) ratios (COX-1/COX-2) indicated the high isoform selectivity of IMTP and IATP for COX-2. Significant levels of (125)I-IMTP and (125)I-IATP were observed in the kidneys and the brain (organs known to express COX-2). The blood clearance of (125)I-IMTP was much faster than that of (125)I-IATP. Distribution of (125)I-IATP to blood cells (88.0%) was markedly higher than that of (125)I-IMTP (18.1%), which was decreased by CA inhibitors. CONCLUSIONS: Our results showed a high inhibitory potency and selectivity of IMTP for COX-2. The substitution of a sulfonamide moiety to a methyl sulfone moiety effectively improved the blood clearance of the compound, indicating the loss of the cross reactivity with CA in (125)I-IMTP. (123)I-IMTP may be a potential SPECT radiopharmaceutical for COX-2 expression.

The Thymidine Phosphorylase Imaging Agent 123I-IIMU Predicts the Efficacy of Capecitabine.

UNLABELLED: Recently, companion diagnostics with nuclear medicine techniques have been anticipated as more suitable means than biopsy for predicting treatment efficacy. The anticancer effect of capecitabine, an orally administered chemotherapeutic agent activated by thymidine phosphorylase (TP), is positively associated with tumor TP expression levels. This study aimed to assess whether TP imaging using a radiolabeled uracil derivative, (123)I-5-iodo-6-[(2-iminoimidazolidinyl)methyl]uracil ((123)I-IIMU), could predict the efficacy of capecitabine treatment. METHODS: Sensitivity to doxifluridine, a metabolite of capecitabine and direct substrate for TP, was assessed by water-soluble tetrazolium salt assays in vitro for 3 human colon cancer cell lines with different TP expression profiles. The intracellular uptake and retention of (123)I-IIMU were evaluated. Mice inoculated with each cell line were treated with capecitabine for 2 wk, and tumor growth was compared. In vivo distribution studies and SPECT/CT imaging of (123)I-IIMU were performed in inoculated mice. RESULTS: In vitro experiments showed a positive relation between TP expression levels and doxifluridine sensitivity. In vitro studies revealed that intracellular uptake and retention of (123)I-IIMU were dependent on TP expression levels. In vivo experiments in inoculated mice showed that (123)I-IIMU accumulation in tumor tissue was in line with TP expression levels and susceptibility to capecitabine treatment. Moreover, SPECT/CT imaging of (123)I-IIMU in tumor-inoculated mice showed that (123)I-IIMU reflects TP expression levels in tumor tissues. CONCLUSION: (123)I-IIMU could be used as an in vivo companion diagnostic for predicting the efficacy of capecitabine treatment.

Relationship between biodistribution of a novel thymidine phosphorylase (TP) imaging probe and TP expression levels in normal mice.

OBJECTIVE: Thymidine phosphorylase (TP) is a key enzyme in the pyrimidine nucleoside salvage pathway and its expression is upregulated in a wide variety of solid tumors. In mice, we previously observed high and specific accumulation levels of our TP imaging probe, radioiodinated 5-iodo-6-[(2-iminoimidazolidinyl)methyl]uracil (IIMU) not only in high-TP-expressing tumors, but also in the liver and small intestine. To clarify the reason for the high accumulation levels of radioiodinated IIMU in the liver and small intestine, we investigated the expression levels of TP in mice in comparison with the biodistribution of radioiodinated IIMU ((123)I-IIMU). METHODS: BALB/cCrSlc mice were injected with (123)I-IIMU, and the radioactivity levels [%ID/g (normalized to a mouse of 25 g body weight)] in the tissues of interest were determined 0.5, 1, 3 and 24 h after the injection (n = 5, each time point). To determine the expression levels of TP, BALB/cCrSlc and ddy mice (n = 3/each strain) were euthanized, and the heart, liver, lung, spleen, kidney, stomach, small intestine, large intestine and brain were collected. The mRNA and protein expression levels of TP in these organs were examined by quantitative reverse transcription-polymerase chain reaction and western blot analyses, respectively. RESULTS: In BALB/cCrSlc mice administered (123)I-IIMU, markedly high radioactivity levels were observed in the liver [1.568 ± 0.237 (%ID/g)] and small intestine [0.506 ± 0.082 (%ID/g)], whereas those in the other tissues were fairly low [<0.010 ± 0.003 (%ID/g)] 30 min after the injection. The highest expression levels of TP mRNA were also observed in the liver and small intestine among the tissues tested. Immunoblotting showed intense immunoreactive bands of the TP protein for the liver and small intestine, whereas no notable bands were detected for other tissues. Similar expression profiles of TP mRNA and protein were observed in ddy mice. CONCLUSION: We confirmed TP expression in various tissues of mice at the mRNA and protein levels: high TP expression levels were observed in the liver and small intestine. These high TP expression levels are consistent with the high accumulation levels of (123)I-IIMU in these tissues. Our results may provide important information about the physiological accumulation of (123)I-IIMU, which may be useful for the clinical diagnostic imaging of TP.

Characteristic brain distribution of 1-(14)C-octanoate in a rat model of focal cerebral ischemia in comparison with those of (123)I-IMP and (123)I-iomazenil.

UNLABELLED: 1-(11)C-Octanoate is a potential tracer for studying astroglial function in PET. To evaluate the usefulness of 1-(11)C-octanoate for studying ischemic stroke, we investigated the brain distribution of 1-(14)C-octanoate and compared it with N-isopropyl-p-(123)I-iodoamphetamine ((123)I-IMP) distribution (cerebral blood flow), (123)I-iomazenil ((123)I-IMZ) distribution (neuronal viability based on (123)I-IMZ binding to benzodiazepine receptors), and hematoxylin-eosin stain (morphologic changes) in a rat model of focal cerebral ischemia. METHODS: The right middle cerebral artery of each rat was occluded intraluminally. The brain distribution of 1-(14)C-octanoate and (123)I-IMP (or (123)I-IMZ) was determined 4 and 24 h after the insult using a dual-tracer autoradiographic technique (n = 4-7 in each group). Coronal brain sections adjacent to those used for autoradiography were stained with hematoxylin and eosin. Regions of interest (ROIs) were determined for 3 coronal slices, and asymmetry indices (AIs, lesion/normal hemisphere) of the tracer uptake were calculated. ROIs on the hemisphere with the lesion were classified into 4 groups: In region A, widespread necrotic cells were observed; in region B, necrotic cells were occasionally observed; in region C1, no morphologic changes were observed and the AIs for (123)I-IMP (or (123)I-IMZ) were 0.8. RESULTS: 1-(14)C-Octanoate uptake decreased in the regions where morphologic changes were observed (regions A and B) but was relatively preserved in the surrounding region without morphologic changes despite reduced (123)I-IMP and (123)I-IMZ uptake (region C1). In the region without morphologic changes (region C1), AIs for 1-(14)C-octanoate were significantly higher than those for (123)I-IMP (4 h, 0.73 +/- 0.23 for 1-(14)C-octanoate and 0.37 +/- 0.20 for (123)I-IMP, P < 0.0001; 24 h, 0.84 +/- 0.11 for 1-(14)C-octanoate and 0.44 +/- 0.15 for (123)I-IMP, P < 0.0001) and those for (123)I-IMZ (4 h, 0.83 +/- 0.19 for 1-(14)C-octanoate and 0.57 +/- 0.13 for (123)I-IMZ, P < 0.0001; 24 h, 0.91 +/- 0.13 for 1-(14)C-octanoate and 0.73 +/- 0.06 for (123)I-IMZ, P < 0.0001). CONCLUSION: 1-(14)C-Octanoate uptake was relatively preserved in the regions without morphologic changes despite reduced (123)I-IMP and (123)I-IMZ uptake. 1-(11)C-Octanoate may provide further functional information on the pathophysiology of ischemic stroke, reflecting astroglial function based on fatty acid metabolism.

In vitro uptake of [1-14C]Octanoate in brain slices of rats: basic studies for assessing [1-11C]Octanoate as a PET tracer of glial functions.

To clarify the contribution of glial cells to octanoate uptake into the brain, we determined the effects of fluoroacetate, a selective inhibitor of glial metabolism, on in vitro brain uptake of [1-14C]octanoate, using rat brain slices. The [1-14C]octanoate uptake significantly decreased, depending on the concentration of fluoroacetate (p = 0.001). The [1-14C]octanoate uptakes at 5 mM (0.23 +/- 0.05% uptake/mg slice) and 25 mM fluoroacetate (0.12 +/- 0.01% uptake/mg slice) were significantly lower than that at control (0.29 +/- 0.02% uptake/mg slice, p < 0.05 and p < 0.001, respectively). The results demonstrate the contribution of glial cells to octanoate uptake into the brain. The potential of [1-11C]octanoate as a PET tracer for studying glial functions is suggested.

A simplified and improved synthesis of [11C]phosgene with iron and iron (III) oxide.

[11C]Phosgene ([11C]COCl2), a useful precursor for labeling several radiopharmaceuticals, is generally produced by catalytic oxidation of [11C]carbon tetrachloride over Fe granules, although in low yields or with poor reproducibility. In order to develop am improved synthesis of [11C]phosgene, two oxidizing agents, Fe2O3 and CuO, were examined. The yield of [11C]phosgene was significantly increased using Fe2O3 powder mixed with Fe granules, while the use of CuO alone, or CuO powder mixed with Fe granules resulted in an insignificant yield. The yield and specific activity of S- (-) [11C]CGP-12177 synthesized using Fe2O3 powder mixed with Fe granules were markedly higher than those synthesized by the previous methods using Fe granules alone or Fe granules mixed with Fe powder. Thus, in the present study, we developed a simple and practical method for the synthesis of [11C]phosgene, which provided an improved yield of S- (-) [11C]CGP-12177.

Chemical impurities in [18F]FDG preparations produced by solid-phase 18F-fluorination.

[18F]FDG was produced by solid-phase 18F-fluorination (resin method) and chemical impurities were determined in the [18F]FDG preparations by ion chromatography. The major chemical impurities were D-glucose (90.5 +/- 6.4 microg/mL), 2-chloro-2-deoxy-D-glucose (11.8 +/- 2.7 microg/mL), and D-mannose (1.7 +/- 0.7 microg/mL), which were expected to be present by considering the synthetic routes. An FDG mass (0.5 +/- 0.2 microg/mL) was also detected in the preparations. No notable radiochemical impurities, including 2-[18F]fluoro-2-deoxy-D-mannose, were detected in the [18F]FDG preparations. Thus, the levels of several chemical impurities were determined in the [18F]FDG preparations produced by solid-phase 18F-fluorination.

Photoinduced transannular reaction of 1,3-dimethylcyclooctapyrimidine-2,4-diones.

This article reports further elaboration of the authors' investigations on the acid-catalyzed photorearrangements undergone by derivatives of 1,3-dimethylcyclooctapyrimidine-2,4-dione. In this case the results are represented for compounds containing a simple methyl or fluorine substituent at different positions in the eight-membered ring. Upon photolysis in frozen benzene containing trifluoroacetic acid, the monomethylated compounds give varying yields of pentalenopyrimidinedione products that are not generated from the fluorinated compounds, which are either inert or undergo hydration accompanied by dehyrofluorination. Plausible mechanisms are advanced to account for the formation of the observed photoproduct species. The work represents an interesting extension and uncovered new aspects of the photorearrangement process.

Synthesis and antiviral activity of novel fluorinated 2',3'-dideoxynucleosides.

A series of 5-(trifluoroethoxymethyl)-2',3'-dideoxyuridines and 5-[bis(trifluoroethoxy)-methyl]-2',3'-dideoxyuridines have been prepared and screened for antiviral activity. The conformations of these compounds are discussed on the bases of NOE studies and the MO calculations. Modelling and NOE studies suggest both syn- and anti conformations for these 5-(2,2,2-trifluoroethoxymethyl)- and 5-[bis(2,2,2-trifluoroethoxy)-methyl]- derivatives. The NOE parameters are also suggested to be more attributable to the nature of the fluorine atom than to structural or conformational changes. Compounds 17, 26 and 30 showed some activity in anti-HIV-1 and anti-HIV-2 assays, but the compounds were devoid of activity against HSV and human rhinovirus. The compounds tested exhibited low cytotoxicity and were inactive against a bank of cancer cells in vitro.

Increased [18F]2-fluoro-2-deoxy-D-glucose ([18F]FDG) yield with recycled target [18O]water: factors affecting the [18F]FDG yield.

The reuse of [18O] water after being purified by distillation has been reported to give lower [18F]2-fluoro-2-deoxy-D-glucose ([18F]FDG) yields, probably due to the presence of organic impurities. In our routine production of [18F]FDG, however, we observed increased [18F]FDG yields with recycled [18O]water. Thus, factors affecting [18F]FDG yield were examined using as-purchased (virgin) and recycled (by photochemical combustion and distillation) [18O]water. [18F]FDG was synthesized by nucleophilic 18F-fluorination on a quaternary 4-aminopyridinium resin. The recycled [18O]water gave an [18F]FDG yield significantly higher than did the virgin water, without any significant difference in the [18F]fluoride yield. Levels of several ionic impurities including Cl- and Ca2+ were significantly higher in the virgin [18O]water than in the recycled water, while significantly larger amounts of organic impurities were detected in the former. Hence, trace amounts of organic impurities were not responsible for the lower [18F]FDG yield. Chloride anion in the [18O]water may compete with [18F]fluoride to lower the [18F]FDG yield.

Radiolabeled uracil derivative as a novel SPECT probe for thymidine phosphorylase: suppressed accumulation into tumor cells by target gene knockdown.

OBJECTIVES: We have developed a radiolabeled uracil derivative, 5-iodo-6-[(2-iminoimidazolidinyl)methyl]uracil (IIMU) as a novel single photon emission computed tomography probe for thymidine phosphorylase (TP). This radioiodinated IIMU has a high affinity for TP and highly accumulates in the TP-expressing tumor cell line A431 (human epidermoid carcinoma). To evaluate the specificity of the cellular uptake of IIMU to TP expression, we examined the effects of TP knockdown on the uptake of ¹²5I-labeled IIMU (¹²5I-IIMU) in the tumor cells. METHODS: TP-specific small interfering RNA (siRNA), glyceraldehyde-3-phosphate dehydrogenase (GAPDH)-specific siRNA (positive control), and negative control siRNA were transfected into A431 cells, respectively. Target-mRNA and protein expression levels of TP and GAPDH were examined 48 and 72 h after transfection, respectively. The cellular uptake level of ¹²5I-IIMU was also evaluated 72 h after transfection. The results were compared after normalization with the corresponding negative controls. RESULTS: After TP-specific and GAPDH-specific siRNA transfection, the expression levels of TP and GAPDH mRNA decreased significantly to 41 and 29%, respectively, compared with the negative control (P<0.001 for both). The expression levels of TP and GAPDH protein also significantly decreased to 34 and 30%, respectively (P<0.001 for both). After TP-specific siRNA transfection, the cellular uptake level of ¹²5I-IIMU decreased significantly to 66% (P<0.001). In contrast, GAPDH siRNA transfection did not significantly affect the cellular uptake level of ¹²5I-IIMU. CONCLUSION: siRNA-mediated TP knockdown significantly decreased the cellular uptake level of ¹²5I-IIMU. This finding indicates that the uptake of IIMU in tumor cells is TP specific and directly corresponds to TP expression levels.

Isolation and identification of new vasodilative substances in diesel exhaust particles.

BACKGROUND, AIM, AND SCOPE: We recently developed a new isolation method for diesel exhaust particles (DEP), involving successive extraction with H(2)O, sodium bicarbonate, and sodium hydroxide, in which the sodium hydroxide extract was found to consist of phenolic components. Analysis of the extract revealed that vasodilative-active nitrophenols are in DEP in significantly higher concentrations than those estimated by an earlier method involving a combination of solvent extraction and repeated chromatography. These findings indicated that our new procedure offers a simple, efficient, and reliable method for the isolation and identification of bioactive substances in DEP. This encouraged us to extend our work toward investigating new vasodilatory substances in the sodium bicarbonate extract. MATERIALS AND METHODS: DEP were collected from the exhaust of a 4JB1-type engine (ISUZU Automobile Co., Tokyo, Japan). GC-MS analysis was performed with a GCMS-QP2010 instrument (Shimadzu, Kyoto, Japan). RESULTS: DEP dissolved in 1-butanol was successively extracted with water, sodium bicarbonate, and then aqueous sodium hydroxide. The sodium bicarbonate extract was neutralized and the resulting mixture of acidic components was subjected to reverse-phase (RP) column chromatography followed by RP-HPLC with fractions assayed for vasodilative activity. This led to the identification of terephthalic acid, p-hydroxybenzoic acid, isophthalic acid, phthalic acid, 3-hydroxy-4-nitrobenzoic acid, 4-hydroxy-3-nitrophenol, and 1,4,5-naphthalene tricarboxylic acid as components of DEP. DISCUSSION: The sodium bicarbonate extract was rich in aromatic carboxylic acid components. Repeated reverse-phase chromatography resulted in the successful isolation of several acidic substances including the new vasodilative materials, 4-hydroxy-3-nitrobenzoic acid, and 3-hydroxy-4-nitrobenzoic acid. CONCLUSIONS: Our new fractionation method for DEP has made possible the isolation of new vasodilative compounds from the sodium bicarbonate extract.

In vitro and in vivo evaluations of a radioiodinated thymidine phosphorylase inhibitor as a tumor diagnostic agent for angiogenic enzyme imaging.

INTRODUCTION: The expression of thymidine phosphorylase (TP) is closely associated with angiogenesis, tumor invasiveness and activation of antitumor agents. We evaluated radioiodinated 5-iodo-6-[(2-iminoimidazolidinyl)methyl]uracil ([(125)I]IIMU) having high TP-inhibitory potency as the new radiotracer for SPECT targeting of TP expression in tumors. METHODS: The characteristics of the radioiodinated TP inhibitor IIMU were determined by evaluating the uptake by tumor cells in vitro and by biodistribution studies in vivo. The distribution of the radiotracer and the extent of TP-specific uptake by tumors were evaluated by a counting method in tumor-bearing mice. RESULTS: The in vitro uptake of radiolabeled IIMU by A431 cells along with high TP expressions was attributed to the binding of the radiotracer to its target enzyme, i.e., TP. In vivo distribution of the radiotracer in A431 tumor-bearing mice revealed tumor/blood and tumor/muscle activity uptake ratios of 36 and 106, respectively, at 3 h after the radiotracer injection. On using low TP-expressing tumors and TP blocking studies as controls, minor TP-specific accumulation of the radiotracer was detected in these studies. CONCLUSION: According to the binding of radioiodinated IIMU to the angiogenic enzyme TP, it can be concluded that radioiodinated IIMU might be suitable as a SPECT tracer for tumor imaging.