13C-urea breath test results in pigs challenged with Helicobacter pylori or other urease producing bacteria

The gastric bacterial flora and its influence on the 13C-urea breath test (UBT) for detection of Helicobacter pylori infection was studied in a pig model. Seven SPF minipigs were used. H. pylori or a mix of other urease positive bacteria were administered orally. UBT, serum and biopsies for histology and culture were collected. Our results show that UBT is not specific for H. pylori in pigs as the gastric bacterial flora is responsible for the high UBT values observed. Furthermore, the Ellegaard Göttingen SPF minipigs are not useful in an animal model for H. pylori studies.

Triazolam-induced modulation of muscarinic acetylcholine receptor in living brain slices as revealed by a new positron-based imaging technique

The effect of triazolam, a potent benzodiazepine (BZ) agonist, on muscarinic acetylcholinergic receptor (mAChR) binding was investigated in living brain slices by use of a novel positron-based imaging technique. Fresh rat brain slices were incubated with [11C]N-methyl-4-piperidylbenzilate ([11C]NMPB), a mAChR antagonist, in oxygenated Krebs-Ringer solution at 37 degrees C. During incubation, time-resolved imaging of [11C]NMPB binding in the slices was constructed on the storage phosphor screens. Addition of triazolam (1 microM) plus muscimol (30 microM), a GABA(A) receptor agonist, to the incubation mixture decreased the specific binding of [11C]NMPB. Ro15-1788, a BZ receptor antagonist, prevented this effect, indicating that the effect was exerted through the GABA(A)/BZ receptor complex. These results demonstrated that stimulation of the GABA(A)/BZ receptor lowers the affinity of the mAChR for its ligand, which may underlie the BZ-induced amnesia, a serious clinical side effect of BZ. No such effect in the P2-fraction instead implies that the integrity of the neuronal cells and/or their environment is prerequisite for the modulation of mAChR by GABA(A)/BZ stimulation.

Evaluation of serology, 13C-urea breath test, and polymerase chain reaction of stool samples to detect Helicobacter pylori in Bangladeshi children

BACKGROUND

Serologic methods to detect Helicobacter pylori in infants, especially in developing countries, may be limited because of decreased immune response caused by malnutrition. The true prevalence may therefore be underestimated in this age group. Urea breath test is considered to be a good screening method in children but is expensive and therefore is not suitable for screening in developing countries. Simple, inexpensive, and accurate noninvasive methods to detect H. pylori in infants and young children are needed.

METHODS

Enzyme immunoassay (EIA) and immunoblot (IB) serologic analyses, 13C-urea breath test (UBT), and immunomagnetic separation--polymerase chain reaction (IMS-PCR) were performed on stool specimens, to detect H. pylori in 68 children between 4 and 24 months of age (mean, 11.5 months) in an endemic area in Bangladesh and the results compared.

RESULTS

The occurrence of H. pylori was 57% (n=39) using only UBT, 60% (n=41) using only IMS-PCR, and 78% (n=53) using UBT and IMS-PCR together. The concordance between UBT and IMS-PCR results was 62%. Immunoblot was positive in only 9% (n=6). Results in all 68 children were negative using EIA.

DISCUSSION

The prevalence of H. pylori infection in this periurban community and age group was high. Only serologic methods seem to be unsatisfactory for screening of H. pylori infection in infants and may not reflect the true prevalence. Immunomagnetic separation-PCR is a simple and rapid method for detection of H. pylori in stool and is an attractive method for analysis of colonization in infants. However, it may reflect a different stage of disease than UBT. Further studies are needed to clarify this.

[Differential diagnosis in adrenal gland tumors using PET and 11C-metomidate]

We have investigated 13 patients with incidentaloma using PET with 11C-metomidate. The patients included six adrenocortical adenomas, one adrenal cancer, two pheochromocytomas, one myelolipoma, one benign cyst and two metastases. A very high tracer uptake was observed in all tumors originating from the adrenal cortex, allowing excellent visualisation, whereas all other processes were negative. PET with 11C-metomidate is a very promising method for the characterisation of incidentalomas and is suggested to be included very early in the evaluation of these patients.

[Positron emission tomography in oncology--an introduction]

Positron emission tomography has developed very much since the start in the late 1970s, especially with the development of new labelling procedures for PET-tracers. With the development of whole body imaging and the discovery that 18F-FDG allows a high sensitivity for the detection of soft tissue tumors, the clinical use has increased remarkably. The cost-effectiveness of this modality, when properly used, has been demonstrated and 18F-FDG-PET should be considered as an early alternative in patient evaluation.

[PET in neuroendocrine tumors]

With the radionuclide tracers available today, 50-90 per cent of neuroendocrine tumours of the gastro-intestinal tract can be visualised with PET (positron-emission tomography). PET also enables the effect of tumour treatment to be monitored in terms of biochemical and functional variables, which is not possible with other radiological techniques. Owing to the very good tumour resolution possible with PET, it serves as a complement to other routine methods such as computed tomography and ultrasonography, and can be used to screen the chest and abdomen for small primary tumours that can not be detected with other methods. In several pre-operative trials PET has been shown to demonstrate more changes in the pancreas and liver than was possible with other methods. In the near future it will be possible to demonstrate the presence of and quantify growth factor receptors, hormones, enzymes, DNA synthesis, mRNA synthesis and protein synthesis. Access to these tumour biological data will be of crucial importance to the individualisation of treatment.

Tissue markers as predictors of postoperative adhesions

BACKGROUND

Postoperative adhesion formation has been associated with a decreased capacity to degrade intra-abdominally deposited fibrin. Adhesions, once lysed, have a high propensity for reformation. This study tested the hypothesis that patients with a high propensity for adhesion formation as well as adhesion tissue had a reduced fibrinolytic capacity.

METHODS

Peritoneal biopsies were taken during abdominal surgery from 21 patients who had previously undergone operation; previously formed adhesion tissue was sampled from ten of these patients. Adhesion formation was scored. The fibrinolytic capacity of peritoneum was determined in tissue extracts.

RESULTS

At the time of opening of the abdominal cavity, levels of plasminogen activator inhibitor (PAI) type 1 (P = 0.009) and tissue-type plasminogen activator (tPA)/PAI complex (P = 0.008) were increased in peritoneal samples from patients with severe adhesions compared with those in samples from patients with less severe adhesions. Adhesion tissue similarly had reduced fibrinolytic capacity as judged by a decrease in tPA activity (P = 0.005) and an increase in PAI-1 level (P = 0.01), reflected in an increased level of tPA/PAI complex (P = 0.008) compared with unaffected peritoneum.

CONCLUSION

These observations demonstrate reduced fibrinolytic capacity in peritoneal tissue in patients with a greater propensity for development of adhesions and likewise in adhesion tissue. This suggests that components of the fibrinolytic system may be used as markers of an increased risk of adhesion development.

Weak affinity chromatography of small saccharides with immobilised wheat germ agglutinin and its application to monitoring of carbohydrate transferase activity

In this work we have evaluated the potential to use wheat germ agglutinin (WGA) for weak affinity chromatography (WAC) of N-acetyl derivatives of mono-, di-, tri- and tetrasaccharides. WGA was used as a ligand in a high performance liquid affinity chromatography (HPLAC) system. Isocratic affinity chromatography was conducted where similar N-acetyl saccharides were separated according to their binding strength to WGA. Affinities are weak and lie typically in the mM range. For example, for 3'sialyllactose, the dissociation constant (Kd) was found to be 2.4 mM at 8 degrees C. It was interesting to note that the WGA-HPLC column can distinguish between the anomeric forms of N-acetylglucosamine. Weak affinity chromatography with immobilised WGA was used in an enzyme assay to detect the activity of GlcNAc-transferases.

One-week treatment with omeprazole, clarithromycin, and metronidazole in children with Helicobacter pylori infection

BACKGROUND

The efficacy of a 1-week "triple therapy" in children with Helicobacter pylori gastritis and recurrent abdominal pain was studied. The effect of treatment was also studied in correlation to recurrent abdominal pain.

METHODS

Thirty-two children with recurrent abdominal pain were investigated with H. pylori serology, 13C-urea breath test, and endoscopy. Gastric biopsy specimens were analyzed with a rapid urease test and histopathology. H. pylori-positive children were treated with omeprazole, clarithromycin, and metronidazole for 7 days. The same treatment was repeated for 2 weeks if a urea breath test produced positive results 1 month after the treatment period. If the test results were still positive after treatment, a second endoscopy was performed with culture.

RESULTS

Twenty-eight (87.5%) children were urea breath test-negative at follow-up 4 weeks (range, 4-15) after treatment. Another child became H. pylori-negative after a second treatment course. Two of the three children who were still positive after the two treatment periods, showed resistance to metronidazole and clarithromycin.

CONCLUSIONS

One-week therapy with omeprazole, clarithromycin and metronidazole is an effective treatment in children with H. pylori infection. Bacterial resistance to clarithromycin and metronidazole must be monitored if treatment fails.

Temporal lobe epilepsy visualized with PET with 11C-L-deuterium-deprenyl--analysis of kinetic data

OBJECTIVES

The purpose of the study was to develop a simplified method for the acquisition and analysis of data from positron emission tomography (PET) using the ligand 11C-L-deuterium-deprenyl. This is motivated by an increased interest in methods to characterize gliosis in neurodegenerative diseases and epilepsy, which can be defined due to an increased expression of the enzyme MAO-B.

METHODS

Seven patients with temporal lobe epilepsy were investigated with PET. The tracer kinetics in different brain structures was recorded and analyzed using different models with and without a plasma input function. The derived values were correlated to literature values of 3H-deprenyl binding in frozen sections from normal human brains.

RESULTS

A good correlation was seen between in vivo binding and in vitro data, with the correlation being equally good irrespective of whether metabolite corrected plasma or modified cerebellar uptake values were used as input function. The epileptic lobe was, compared to non-epileptic, characterized by a lower initial distribution and an enhanced late accumulation of the tracer. With the applied method, it was possible to correctly identify the epileptic side in all 6 unilateral patients and I probable bilateral case.

CONCLUSIONS

PET with 11C-L-deuterium-deprenyl gives a good correlation between calculated in vivo binding and MAO-B activity. The analysis can be simplified and blood sampling avoided if modified cerebellar time-activity data is used as a reference. Separate images of distribution volume and MAO-B binding can be generated.

In vitro evaluation of 11C-labeled (S)-nicotine, (S)-3-methyl-5-(1-methyl-2-pyrrolidinyl)isoxazole, and (R,S)-1-methyl-2-(3-pyridyl)azetidine as nicotinic receptor ligands for positron emission tomography studies

The binding characteristics of the novel 11C-labeled nicotinic ligands (R,S)-1-methyl-2-(3-pyridyl) azetidine (MPA) and (S)-3-methyl-5-(1-methyl-2-pyrrolidinyl)isoxazole (ABT-418) were investigated in comparison with those of (S)-[11C]nicotine in vitro in the rat brain to be able to predict the binding properties of the new ligands for positron emission tomography studies in vivo. The data from time-resolved experiments for all ligands indicated fast binding kinetics, with the exception of a slower dissociation of [11C]MPA in comparison with (S)-[11C]nicotine and [11C]ABT-418. Saturation experiments revealed for all ligands two nicotinic receptor binding sites with affinity constants (K(D) values) of 2.4 and 560 nM and binding site densities (Bmax values) of 65.5 and 223 fmol/mg of protein for (S)-[11C]nicotine, K(D) values of 0.011 and 2.2 nM and Bmax values of 4.4 and 70.7 fmol/mg of protein for [11C]MPA, and K(D) values of 1.3 and 33.4 nM and Bmax values of 8.8 and 69.2 fmol/mg of protein for [11C]ABT-418. In competing with the 11C-ligands, epibatidine was most potent, followed by cytisine. A different rank order of potencies was found for (-)-nicotine, (+)-nicotine, MPA, and ABT-418 displacing each of the 11C-ligands. Autoradiograms displayed a similar pattern of receptor binding for all ligands, whereby [11C]MPA showed the most distinct binding pattern and the lowest nonspecific binding. We conclude that the three 11C-labeled nicotinic ligands were suitable for characterizing nicotinic receptors in vitro. The very high affinity of [11C]MPA to nicotinic acetylcholine receptors, its low nonspecific binding, and especially the slower dissociation kinetics of the [11C] MPA from the putative high-affinity nicotinic acetylcholine receptor binding site compared with (S)-[11C]nicotine and [11C]ABT-418 raise the level of interest in [11C]MPAfor application in positron emission tomography.

[PET as a tool in pharmacologic development]

Positron emission tomography (PET) allows the in vivo recording of tracer compounds with respect to anatomical distribution, time course and absolute concentration. These features has proven of great value in drug development, especially in the phase of early clinical trials. PET can be used to assess the tissue kinetics of a new drug, or to evaluate a drugs interaction with a target system and thereby aid in decisions regarding dosing regimes.

In vitro and in vivo characterization of (+)-3-[11C]cyano-dizocilpine

(+)-3-[11C]Cyano-5-methyl-10,11 -dihydro-5H-dibenzo[a,d]-cyclohepten-5,10-imine ([11C]MKC) was successfully synthesized as a potential radiotracer for PET studies on the NMDA receptor channel complex. In vitro binding properties of [11C]MKC were investigated with newly developed techniques for efficient evaluation of 11C-labeled compounds. The association curve of [11C]MKC binding in rat forebrain membranes showed that the specific binding reached an equilibrium within 30 min. Specific binding was saturable with affinity constant KD=8.2+/-0.4nM and Bmax=1.62+/-0.04 pmol/mg protein with glutamate and glycine included in the incubation medium. The binding of [11C]MKC was decreased by extensive washing of the membrane preparation. (+)- and (-)-Dizocilpine, 3-cyano-dizocilpine, and ketamine inhibited the specific binding of [11C]MKC with IC50 values of 37.3, 445.0, 65.8nM and 3.91 microM, respectively. High specific binding in in vitro autoradiography was distributed predominantly in telencephalic regions (the hippocampus, cerebral cortex, and striatum) followed by thalamus. PET studies using rhesus monkeys under anesthesia showed high uptake of [11C]MKC in the temporoparietal and frontal cerebral cortices, striatum, and thalamic regions, although it is problematic to verify the specific binding in vivo by PET.

In vitro and animal validation of bromine-76-bromodeoxyuridine as a proliferation marker

The potential of 76Br-bromodeoxyuridine as a PET tracer for characterizing proliferation potential was investigated in multicellular tumor aggregates and in healthy rats and pigs.

METHODS

Bromine-76-bromide was produced by proton irradiation of a 76Se-enriched target using a 17-MeV cyclotron and recovered by thermal diffusion. Bromine-76-BrdU was prepared from the corresponding trimethylstannate by an oxidative bromination. Multicellular aggregates from a carcinoid cell line and two bladder cancer cell lines were co-incubated with 76Br-BrdU and 3H-thymidine and the uptake and DNA incorporation analyzed. About 0.5 MBq 76Br-BrdU were injected in the tail vein of unanaesthetised Sprague-Dawley rats. Two to 36 hr later they were decapitated and the radioactivity concentration and fraction of radioactivity incorporated into DNA determined in five different organs and the blood. Parallel studies were performed in animals pretreated with hydroxyurea. In separate experiments, rats were given an injection of 76Br-bromide and organ uptake was evaluated after 20 hr. PET studies were performed in two pigs and the uptake in different organs was investigated after injection of 76Br-BrdU. In these studies, diuresis was induced by furosemide and mannitol and radioactivity in blood and organs was followed during 10 hr.

RESULTS

In the cell aggregates, 30%-90% of the radioactivity was extracted in the DNA fraction. A good correlation was found between 76Br-BrdU and 3H-thymidine with respect to total uptake and DNA fraction. The DNA fraction increased from 2-10 hr after incubation. With in vivo injection in the rat, relatively high uptake of radioactivity was found in all organs, unrelated to the degree of DNA synthesis. However, inhibition by hydroxyurea occurred only in the spleen and intestines, organs which also showed a high degree of incorporation of 76Br-BrdU into DNA. In the pig, the highest in vivo uptake was observed in the red bone marrow and the intestines. In these organs, 70%-80% of the radioactivity was recovered in the DNA fraction. The concentration of radioactivity in the heart, liver and kidney was 3-10 times lower, and here the DNA fraction accounted for 10%-20% of the radioactivity. The decay-corrected radioactivity in blood and nonproliferating organs decreased with diuresis with a half-life of 13 and 16 hr, respectively.

CONCLUSION

It is suggested that the radioactivity uptake as seen after the administration of 76Br-BrdU, is constituted by two parts: one relating to incorporation into DNA and one existing as free 76Br- or metabolites of 76Br-BrdU. If sufficient time has passed, 76Br- dominates other metabolites. A correct assessment of DNA-incorporated radioactivity using PET with 76Br-BrdU is not trivial and can only be made with due correction for 76Br-, using either a complementary investigation after hydroxyurea pretreatment (in animal studies) or a separate 76Br-bromide investigation. Alternatively, the free bromide can be eliminated partially through forced diuresis.

Positron emission tomography with 5-hydroxytryprophan in neuroendocrine tumors

PURPOSE

Carcinoid tumors, especially those of midgut origin, produce serotonin via the precursors tryptophan and 5-hydroxytryptophan (5-HTP). We have evaluated the usefulness of positron emission tomography (PET) with carbon-11-labeled 5-HTP in the diagnosis and treatment follow-up evaluation of patients with neuroendocrine tumors.

PATIENTS AND METHODS

PET using 11C-labeled 5-HTP was compared with computed tomography (CT) in 18 patients (14 midgut, one foregut, one hindgut carcinoid, and two endocrine pancreatic tumors [EPT]). In addition, 10 of 18 patients were monitored with PET examinations during treatment.

RESULTS

All 18 patients, including two with normal urinary 5-hydroxyindole acetic acid (U-5-HIAA), had increased uptake of 11C-labeled 5-HTP in tumorous tissue as compared with normal tissue. Liver metastases, as well as lymph node, pleural, and skeletal metastases, showed enhanced 5-HTP uptake and PET could detect more lesions than CT in 10 patients and equal numbers in the others. Tumor visibility was better for PET than for CT due to the high and selective uptake of 5-HTP with a high tumor-to-background ratio. Binding studies indicated an irreversible trapping of 5-HTP in the tumors. Linear regression analyses showed a clear correlation (r = .907) between changes in U-5-HIAA and changes in the transport rate constant for 5-HTP during treatment.

CONCLUSION

PET with 11C-labeled 5-HTP demonstrated high uptake in neuroendocrine gastrointestinal tumors and thereby allowed improved visualization compared with CT. The in vivo data on regional tumor metabolism, as expressed in 11C-5-HTP uptake and transport rate, provided additional information over conventional radiologic techniques. The close correlation between the changes in 11C-5-HTP transport rate and U-HIAA during medical treatment indicates the potential of 11C-5-HTP-PET as a means to monitor therapy.

Synthesis, in vivo rhesus monkey biodistribution and in vitro evaluation of a 11C-labelled potent aromatase inhibitor: [N-methyl-11C]vorozole

[N-methyl-11C]Vorozole, a high-affinity aromatase-binding radiotracer, was synthesized through N-methylation of the corresponding nor-vorozole derivative using [11C]methyl iodide. [N-methyl-11C]Vorozole was obtained in 53-56% radiochemical yield based on [11C]methyl iodide within 40 min of the end of radionuclide production. The final formulation was >98% radiochemically pure and had a specific radioactivity of 10-143 GBq/micromol. In vitro, [N-methyl-11C]vorozole displayed high and specific binding to aromatase-rich human placenta. [N-methyl-11C]Vorozole binding to other tissues was lower and less specific. The dissociation constant measured was in the low nM range (Kd 1.7 nM), consistent with published Ki values for vorozole. Biodistribution studies in rhesus monkeys showed high liver uptake, which reached a constant level of 20% of the injected dose after 10 min, and an otherwise relatively even distribution of radioactivity. Pretreatment with vorozole only caused minor alterations of the biodistribution of the tracer.

N-[11C]methylspiperone PET, in contrast to [11C]raclopride, fails to detect D2 receptor occupancy by an atypical neuroleptic

The occupancy of the atypical neuroleptic quetiapine (Seroquel) at the D2 dopamine receptor was investigated using the PET tracers [11C]raclopride and N-[11C]methylspiperone in a group of five schizophrenic patients. A steady-state treatment condition was ensured by dosing the patients with 750 mg quetiapine daily during 3 weeks followed by a period of tapering off the dose. For each patient, PET examinations were performed with both tracers at two of the following doses: 750, 450, 300 and/or 150 mg. As control, a group of six healthy untreated volunteers was investigated. The D2 binding potential in the putamen and the caudate nucleus was determined by using an evaluation method based on the method proposed by Patlak and Blasberg. The receptor occupancy was determined by assuming that the group of healthy volunteers is representative of untreated drug-naive schizophrenic patients. While a significant linear trend of increasing occupancy with increasing quetiapine dose (reaching 51% +/- 10% occupancy at the 750 mg dose) was detected with [11C]raclopride (P < 0.01), no such trend was apparent for N-[11C]methylspiperone (P > 0.09, maximal occupancy values were 2% +/- 3%, measured for the group of three patients on 450 mg). The study suggests that N-[11C]methylspiperone cannot be used for the assessment of D2 receptor occupancy induced by quetiapine. The result is discussed in terms of endogenous dopamine, tracer kinetics and equilibrium dissociation constants.

Treatment of Helicobacter pylori infection in infants in rural Bangladesh with oral immunoglobulins from hyperimmune bovine colostrum

BACKGROUND

Antibodies from hyperimmune bovine colostrum have been shown to be effective in treatment against a variety of microorganisms, including Helicobacter pylori in adults.

AIM

To test this form of treatment in a small group of H. pylori infected children in a periurban community in Bangladesh.

METHODS

Twenty-four infants, 4-29 months old (mean age 16.5+/-7.7 months) and infected with H. pylori, were treated with purified immunoglobulins from hyperimmune bovine colostrum for 1 month, in a placebo-controlled, double-blind pilot study. Diagnosis was established with 13C-urea breath test (UBT) before and after the treatment period and at a 1-month follow-up.

RESULTS

None of the hyperimmune bovine colostrum-treated children became UBT negative. Five children initially positive in the UBT screening spontaneously became negative by the start of the study with hyperimmune bovine colostrum/placebo. At the end of the 1-month study period, three had became positive again.

CONCLUSION

Hyperimmune bovine colostrum does not eradicate H. pylori infection in infants. Transient H. pylori infection is common among infants in high endemic areas, as is reinfection after clearance. This presents obstacles to evaluation of therapeutic investigations in young children in areas where H. pylori is prevalent.

In vitro and in vivo primate evaluation of carbon-11-etomidate and carbon-11-metomidate as potential tracers for PET imaging of the adrenal cortex and its tumors

METHODS

With the purpose of developing a PET imaging agent for tumors of the adrenal cortex, we developed syntheses for 11C-etomidate and its methyl analog, 11C-metomidate. (R)-[O-ethyl-1-11C]Etomidate and (R)-[O-methyl-11C]metomidate were prepared by reaction of the appropriate respective 11C-labeled alkyl iodide and the tetrabutylammonium salt of the carboxylic acid derivative. The specificity of binding to the adrenal cortex was tested through the use of frozen section autoradiography of different tissues of the rat, pig and human. Inhibition of tracer binding was evaluated with etomidate, ketoconazole and metyrapone, well-known inhibitors of enzymes for steroid synthesis. Tracer binding to different human tumor samples was compared to immunohistochemical staining with antibodies for the steroid synthesis enzymes P450 11beta (11beta-hydroxylase), P450 scc (cholesterol side-chain cleavage enzyme), P450 C21 (21 -hydroxylase) and P450 17alpha (17alpha-hydroxylase). Three PET investigations, one with 11C-etomidate and two with 11C-metomidate, were performed in rhesus monkey sections, including the adrenals, liver and kidneys. Time-activity curves were generated from measured tracer uptake in these organs.

RESULTS

In frozen section autoradiography of various tissues, high binding was seen in the adrenal cortex from all species, as well as in the tumors of adrenal cortical origin. The level of liver binding was about 50% of that in the adrenals, whereas that of all other organs was <10% of the adrenal binding. The adrenal binding was blocked by etomidate and ketoconazole at low doses but not by metyrapone. The binding in the adrenal tumor samples correlated with immunostaining for P450 11beta . PET studies in the monkey demonstrated high uptake in the adrenals with excellent visualization. The uptake increased with time without indication of washout. Slightly lower uptake was seen in the liver as compared to the adrenals, and in the late images, no organs other than adrenals and liver were seen.

CONCLUSION

These investigations indicate that 11C-etomidate and 11C-metomidate have the potential to be useful specific agents for the visualization of the normal adrenal cortex and to provide positive identification of adrenal cortical tumors.

Synthesis and in vitro evaluation of [carbonyl-11C]estramustine and [carbonyl-11C]estramustine phosphate

[carbonyl-11C]Estramustine and [carbonyl-11C]estramustine phosphate were synthesized from [11C]phosgene using a one pot procedure. [carbonyl-11C]Estramustine was obtained in 31-43% decay corrected yield based on radioactivity trapped in the reaction vessel. The product was obtained 25 min after the end of radionuclide production with a specific radioactivity of 0.38-1.11 Ci/mumol. A method was developed yielding [carbonyl-11C]estramustine phosphate in 29-45% decay corrected yield based on trapped radioactivity, without purification of the [carbonyl-11C]estramustine intermediate. The product was obtained within 40 min of the end of radionuclide production with a specific radioactivity of 0.59-0.86 Ci/mumol. Results from in vitro experiments suggest that because of their high nonspecific binding, the compounds are unsuitable for positron emission tomography as imaging agents for the estramustine binding protein in cancer.

Skeletal metastases from breast cancer: uptake of 18F-fluoride measured with positron emission tomography in correlation with CT

OBJECTIVE

To characterise the uptake of 18F in skeletal metastases from breast cancer using positron emission tomography (PET) and to relate these findings to the appearance on CT.

PATIENTS AND DESIGN

PET with 18F and CT were performed in five patients with multiple skeletal metastases from breast cancer. The CT characteristics were analysed in areas with high uptake on the PET study. Dynamic PET imaging of the skeletal kinetics of the 18F-fluoride ion were included.

RESULTS

The areas of abnormal high accumulation of 18F correlated well with the pathological appearance on CT. Lytic as well as sclerotic lesions had markedly higher uptake than normal bone, with a 5-10 times higher transport rate constant for trapping of the tracer in the metastatic lesions than in normal bone.

CONCLUSION

PET with 18F-fluoride demonstrates very high uptake in lytic and sclerotic breast cancer metastases.

Time course of central nervous dopamine-D2 and 5-HT2 receptor blockade and plasma drug concentrations after discontinuation of quetiapine (Seroquel) in patients with schizophrenia

Quetiapine (Seroquel) is a novel antipsychotic with an atypical profile in animal models and a relatively short plasma half-life of 2.5 5 h. In the present study, we used PET to compare the time course of blockade of dopamine D2 and serotonin 5HT2 receptors of quetiapine using C11-raclopride and C11-N-methyl-spiperone as ligands, parallel to monitoring plasma drug concentrations. It was an open study in 11 schizophrenic men using a fixed dose of 450 mg quetiapine. Eight men completed the 29 days treatment, followed by four PET scans performed over a 26-h period after withdrawal of the compound. Quetiapine was shown to bind to dopamine D2 receptors in striatum and 2 h (t[max]) after the last dose, 44% receptor occupancy was calculated. After 26 h it had dropped to the same level as was found in untreated healthy volunteers. Serotonin 5HT2 receptor blockade in the frontal cortex was 72% after 2 h, which declined to 50% after 26 h. The terminal plasma half-life of quetiapine was 5.3 h. Clinically, our eight patients had good antipsychotic effect without any extrapyramidal side-effects. Our data shows that quetiapine has a relatively low affinity for dopamine D2 receptors, with an occupancy half-life (10 h), which was about twice as long as that for plasma. A more prolonged blockade of the serotonin 5HT2 receptors was found in the frontal cortex, with receptor occupancy half-life of 27 h. Compared to clozapine, as demonstrated in other studies, quetiapine has much the same ratio of D2/5HT2 occupancy. This could suggest that the combination of D2/5HT2 receptor blockade contributes to the antipsychotic effect and a low incidence of EPS seen with quetiapine in comparative phase three trials. Our results also confirm the clinical data that quetiapine can be administered twice daily.