Practice nurses and the effects of the new general practitioner contract in the British NHS: the advent of a professional project? National Health Service

Interposition of a metabolizable linkage has been performed to reduce the hepatic radioactivity levels of radiolabeled antibodies. To estimate the validity of this strategy, a radioiodination reagent (HML) that provides a stable attachment for m-iodohippuric acid with proteins in plasma while facilitating rapid and selective release of the compound after lysosomal proteolysis in the liver was conjugated with a monoclonal antibody (mAb) against osteogenic sarcoma (OST7, IgG1). Radiolabeled OST7 conjugates with a plasma-labile ester bond for releasing m-iodohippuric acid (MIH), plasma-stable amide bonds for releasing radiometabolites of hepatobiliary excretion (MPH), or slow elimination rates from hepatocytes ([111In]EMCS-Bz-EDTA) were prepared with similar conjugation chemistry. The four radiolabeled OST7 conjugates were characterized both in vitro and in vivo. All the radiolabeled OST7 conjugates had similar radiochromatograms on size-exclusion HPLC and similar antigen binding affinities. While MIH-OST7 indicated accelerated clearance of radioactivity from the blood due to the release of m-iodohippurate, the rest of the three radiolabeled OST7 conjugates remained stable in serum incubation studies and had similar radioactivity elimination from the blood in vivo. When injected into normal mice, HML-OST7 demonstrated tissue-to-blood ratios of radioactivity similar to those of MIH-OST7 and significantly lower than those of the other two radiolabeled OST7 conjugates. In biodistribution studies in nude mice, both HML-OST7 and MIH-OST7 exhibited tumor-to-liver or tumor-to-intestine ratios of radioactivity higher than those of [111In]EMCS-Bz-EDTA-OST7 or MPH-OST7, respectively. HML-OST7, MPH-OST7, and [111In]EMCS-Bz-EDTA-OST7 indicated there were no changes in the radioactivity levels in the tumor between 24 and 48 h postinjection, whereas MIH-OST7 significantly decreased the radioactivity levels in the tumor at these time points. HML reduced the radioactivity levels in nontarget tissues without impairing the tumor radioactivity levels delivered by OST7. These findings indicated that the design of a radiolabeled mAb that is stable in plasma and liberates the radiometabolite of rapid urinary excretion constitutes an effective strategy for achieving target-selective radioactivity delivery.     

Nitric oxide: a biological effector. Detection using electron paramagnetic resonance

The synthesis and preliminary biological characterization of two isomeric technetium labeled complexes (2,5,5,9-tetramethyl-4,7-diaza-7-(3' (R)-quinuclidinylcarboxymethyl)-2,9-decanedithiolato oxo 99/99mtechnetium(V), [99/99mTc]-1 and [99/99mTc]-2) designed to exhibit affinity to muscarinic cholinergic receptors are described. In vitro binding assays were conducted in mouse brain homogenates (whole brain-cerebellum) at 37 degrees C by the centrifugation method, where non-specific binding was defined by atropine (1 microM). The measured affinity (KD) of [99Tc]-1 for mAChR was 1.9 +/- 0.5 microM (mean +/- SEM; n = 3) and [99Tc]-2 was 4.5 +/- 0.5 microM (mean +/- SEM; n = 3). Scatchard analysis indicated that Bmax values were 10.6 +/- 0.5 and 16.9 +/- 0.5 pmol/mg tissue, respectively. In competition assays, [99Tc]-1 exhibited an apparent affinity (KI) of 16.5 microM (n = 2) against [125I] iododexetimide, whereas [99Tc]-2 exhibited an affinity (KI) of 105 microM. In vivo, 0.3% of the injected dose of [99mTc]-1 and [99mTc]-2 accumulated in the brain at 5 min after injection. These values indicate technetium analogues of neuroreceptor binding ligands can be synthesized and retain some affinity for the receptor.     

Novel 99mTc aminobisthiolato/monothiolato "3 + 1" mixed ligand complexes: structure-activity relationships and preliminary in vivo validation as brain blood flow imaging agents

A series of neutral, lipophilic 99mTc mixed-ligand complexes of the general formula 99mTcOL1L2, where L1H2 is an N-substituted bis-(2-mercaptoethyl)amine, [X-CH2CH2N(CH2CH2SH)2], [SNS], and L2H is a monodentate thiol (RSH), [S], has been synthesized and evaluated in rodents for potential use in brain blood flow imaging. The complexes were prepared by ligand exchange reaction using 99mTc(V)O-glucoheptonate as precursor and equimolar quantities of the two ligands. In all cases the syn isomer was formed in a high yield, whereas the anti isomer was not always present. The formation of two isomeric complexes-syn and anti-was expected, since the N-substituent (X-CH2CH2N) can assume syn or anti configuration with respect to the 99mTcO3+ core during complexation. One anti and all syn isomers were isolated by HPLC. Their identity was confirmed by comparative HPLC studies with the analogous 99Tc complexes of established structure. In vivo distribution, in particular brain uptake and retention, greatly depended on the type of either tridentate (L1H2) or monodentate (L2H) ligand. All 99mTc complexes showed significant brain uptake in mice (0.78-4.35% injected dose per organ at 5 min postinjection). This initial uptake remained nearly constant for at least 30 min for most of the complexes. Structure-activity relationships of novel 99mTc(V)O SNS/S complexes in mice are reported and discussed. Selected complexes were further studied in rats. High brain uptake, comparable to that of 99mTc-d,l-HMPAO, and sufficient retention 60 min postinjection were provided with complex 18 [X = (C2H5)2N and R = p-CH3OC6H4CH2].     

Inhibition of pulmonary eosinophilia in P-selectin- and ICAM-1-deficient mice

Potent antagonists of bombesin-like peptides have shown great potential for applications in cancer therapy. A 99mTc-labeled agent capable of identifying patients who could benefit from these emerging therapies would have a great impact on patient management. This study involves the synthesis and initial evaluation of technetium diaminedithiolate analogues derived from the potent bombesin analogue Pyr-Gln-Lys-Leu-Gly-Asn-Gln-Trp-Ala-Val-Gly-His-Leu-Met-NH2 (Lys3-bombesin). We coupled two diaminedithiol (DADT) bifunctional chelating agents (BCAs 1 and 2) to the Lys3 residue at the N-terminal region that is not required for binding to the receptor. 99mTc labeling was performed by ligand exchange on addition of [99mTc]glucoheptonate to a solution of the adduct at room temperature. Two products were obtained from each adduct on analysis by HPLC. The major to minor product ratios of the 99mTc-labeled analogues were 3:1 for products from BCA 1 and 9:1 for the products from BCA 2. Macroscopic amounts of the 99Tc analogues were similarly prepared using [99Tc]glucoheptonate. In this case, the major to minor ratios were 2:1 for the products from both BCAs. For initial evaluation of the binding of the Tc-labeled peptides to bombesin receptors, the 99Tc analogues were used in vitro in competitive binding assays in rat brain cortex membranes against [125I-Tyr4]bombesin. Results of the in vitro assays showed that the inhibition constants (Ki) of the major and minor products were 3.5+/-0.7 and 3.9+/-1.5 nM, respectively, for the products from BCA 1; and 7.4+/-2.0 and 5.2+/-1.5 nM for the products derived from BCA 2, respectively. The high affinity exhibited by these technetium analogues is an indication of their potential for use in non-invasive in vivo biochemical characterization of cancers that possess receptors for bombesin.     

Temporal and spatial expression of the E5a protein during the differentiation-dependent life cycle of human papillomavirus type 31b

Nalpha-for-Nle-Leu-Phe-Nle-Tyr-Lys, a chemotactic peptide that binds with high affinity to the chemoattractant receptor on granulocytes and monocytes, was labeled with 99mTc using the diaminedithiol (DADT) chelating system to coordinate the Tc. 99mTc labeling of the DADT-coupled peptide was accomplished in 84% overall yield (room temperature for 10 min) using [99mTc]glucoheptonate as the donor of prereduced Tc. HPLC analysis showed two major 99mTc-labeled peptide peaks, 99mTc-DADT-Pep-I and 99mTc-DADT-Pep-II, were obtained in a ratio of 1:0.85. Using an iodoacetamide-derivatized gel to remove unlabeled peptide from the 99mTc labeling mixtures, essentially no-carrier-added (nca) high-specific activity 99mTc-labeled chemotactic peptides were obtained. The 99Tc analogues of the peptides were synthesized (72% yield) in a similar fashion and correlated with 99mTc complexes I and II by HPLC. In vitro competitive receptor binding assays of the isolated 99Tc analogues were performed against the tritiated chemotactic peptide [3H]N-for-Met-Leu-Phe ([3H]fMLF) using isolated granulocytes. The 99Tc-derivatized peptides showed similar binding affinities to the chemoattractant receptor as the unlabeled Nalpha-for-Nle-Leu-Phe-Nle-Tyr-Lys. The nca 99mTc-labeled peptides gave high contrast images of experimental inflammation in rabbits without causing neutropenia. Thus, it is feasible to attach the Tc-DADT chelate to low-molecular weight receptor binding chemotactic peptides and retain substantial binding to the receptor. Chemotactic peptides labeled with 99mTc via the DADT ligand system have the potential for imaging focal sites of inflammation without toxic effects, an important consideration in the successful utilization of chemotactic peptide agonists.     

Comparative study in vivo and in vitro of uniformly 14C-labelled and 125I-labelled recombinant fibroblast growth factor 2

Recombinant bovine fibroblast growth factor (FGF2), uniformly labelled with 14C ([14C]FGF2), was purified and showed to be highly stable and to retain full biological activity. Organ distribution of [14C]FGF2 after intravenous injection of young rats was assessed by autoradiography of whole body sections and compared with those obtained with [125I]iodinated FGF2 (125I-FGF2). Thyroid, stomach, intestine, bladder and skin were radioactively labelled only in the case of 125I-FGF2. This tissue-labelling is artefactual, probably due to free iodide binding not observed when using [14C]FGF2. High-resolution autoradiography showed a complex tissue distribution of [14C]FGF2 in kidney and adrenal organs. Incubation of frozen eye sections with [14C]FGF2 showed a specific and high-resolution labelling pattern of ocular tissues. After cellular internalization, [14C]FGF2 was processed into five distinct polypeptides of 16, 14, 8, 7, and 5.5 kDa. The 14-kDa and 7-kDa polypeptides are novel catabolic fragments not detected with radioiodinated FGF2. In terms of stability, tissue distribution specificity, and autoradiographic resolution, [14C]FGF2 proved to have more advantages than 125I-FGF2 for pharmacokinetic and catabolism studies.     

New and versatile ternary ligand system for technetium radiopharmaceuticals: water soluble phosphines and tricine as coligands in labeling a hydrazinonicotinamide-modified cyclic glycoprotein IIb/IIIa receptor antagonist with 99mTc

A hydrazinonicotinamide-functionalized cyclic platelet glycoprotein IIb/IIIa (GPIIb/IIIa) receptor antagonist [cyclo(D-Val-NMeArg-Gly-Asp-Mamb(5-(6-(6-hydrazinonicotin amido) hexanamide))) (HYNIC-tide)] was labeled with 99mTc using tricine and a water soluble phosphine (TPPTS, trisodium triphenylphosphine-3,3',3"-trisulfonate; TPPDS, disodium triphenylphosphine-3,3'-disulfonate; or TPPMS, sodium triphenylphosphine-3-monosulfonate] as coligands. The synthesis of technetium complexes, [99mTc(HYNICtide)(L)(tricine)] (1, L = TPPTS; 2, L = TPPDS; 3, L = TPPMS), can be performed in one or two steps in high yield and with high specific activity (> or = 20,000 Ci/mmol). For example, the reaction of the HYNICtide, [99mTc]pertechnetate, stannous chloride, and tricine at pH 4-5 and room temperature results in the complex [99mTc(HYNICtide)(tricine)2], which reacts with TPPTS (50 degrees C for 30 min) to give complex 1 in > or = 90% yield as determined by radio-HPLC. Complexes 1-3 are formed as equal mixtures of two isomeric forms and are stable for > or = 6 h in the reaction mixture and in dilute solution. Both isomeric forms of complex 1 were found by a platelet-binding assay to contain the 99mTc-labeled HYNICtide and possess biological activity. The composition of these complexes was determined to be 1:1:1:1 for Tc:HYNICtide:L:tricine through a series of mixed ligand experiments on the tracer (99mTc) level. Surprisingly, this composition is maintained over a wide range of relative ligand ratios. The relative bonding capability of the three phosphine coligands to the Tc was determined by spiking various amounts of TPPDS or TPPMS into TPPTS and falls in the order TPPMS > TPPDS > TPPTS. The lipophilicity of the [99m Tc]HYNICtide complexes can be systematically varied by the choice of the phosphine and aminocarboxylate coligands. Using the combination of tricine and a phosphine ligand, HYNIC-derivatized peptides or other small molecules can be labeled with 99mTc in high specific activity and with high stability for potential use as radiopharmaceuticals.     

Evaluation of [14C]aminopyrine breath test, peripheral clearance of [99mTc]EHIDA, and serum bile acid levels in liver function and disease

The purpose of this study is to evaluate the diagnostic value of the following tests in the assessment of patients with chronic liver disease (CLD) and cholestatic syndrome (CS): (1) aminopyrine breath test, measuring 14CO2 excretion in the expired air, (2) peripheral clearance of [99mTc]EHIDA, and (3) postprandial levels of glycocholic acid (GCA) and glycochenodeoxycholic acid (GCDCA). The results indicate that: (1) 14CO2 2-hr excretion rate is a specific and sensitive marker of liver function, with good correlation with postprandial bile acid levels, [99mTc]EHIDA retention, and the conventional tests of serum albumin and prothrombin time. (2) Peripheral clearance and retention of [99mTc]EHIDA increased in both groups of CLD and CS vs controls, but it does not discriminate between the two. (3) Postprandial bile acids were elevated in CLD, particularly those of GCDCA, whereas GCA levels were significantly elevated in CS compared with CLD. This may be due to increased synthesis and entry into the blood. (4) The combination of [14C]aminopyrine breath test and postprandial levels of GCDCA enhance the diagnostic value, specificity, and sensitivity in the assessment of patients with CLD.     

Imaging experimental osteomyelitis using radiolabeled liposomes

We evaluated radiolabeled liposomes (liposomes labeled both with 99mTc and 111In) for the early detection of osteomyelitis in an experimental model. METHODS: Liposomes, containing 5% polyethylene glycol-distearoyl phosphatidylethanolamine with encapsulated glutathione and deferoxamine, were prepared and labeled with 99mTc and 111In by a previously described method. Acute osteomyelitis was induced in male New Zealand rabbits by intramedullary injection of sodium-morrhuate and Staphylococcus aureus in the tibial bone marrow. Serial imaging studies, consisting of radiolabeled liposome imaging (2-4 mCi 99mTc and 75-125 microCi 111In), 99mTc-methylene diphosphonate (MDP) (3-5 mCi) and 67Ga-citrate (500 microCi), were performed starting at the third day after injection. Each radionuclide study was separated by at least 2 days. The animals also underwent radiography of the lower extremities. The animals were then killed and the infected tibia was excised for histopathology. RESULTS: For interpreting relative efficacy of individual radiopharmaceuticals, only animals showing positive histopathological findings (n = 9) were considered. Radiographs (Days 12, 13) were conclusive for osteomyelitis in only 3 rabbits. Radiolabeled liposome imaging (Days 4-6) showed positivity in 8 cases and was equivocal in 1. Though the lesion could be delineated as early as 8 hr postinjection in the 99MTc window, the best target-to-nontarget ratio (T/NT) of 1.86 +/- 0.19 was obtained at 48 hr in the 111In window. Three-phase 99mTc-MDP scan (Day 7) was positive in only 5 rabbits with 3 hr T/NT of 1.6 +/- 0.23. Galium-67-citrate images (Days 9-11) were positive in 8 cases and equivocal in 1, the mean 48 hr T/NT being 1.74 +/- 0.24. These results show liposomes are better than 99mTc-MDP for imaging bone infection. Given the early localization and better quality of the images, radiolabeled liposomes also exhibited advantages over 67Ga-citrate for detection of acute osteomyelitis.     

Injury probability and risk in frontal crashes: effects of sorting techniques on priorities for offset testing

A hydrazinonicotinamide-functionalized cyclic platelet glycoprotein IIb/IIIa (GPIIb/IIIa) receptor antagonist [HYNICtide, cyclo(D-Val-NMeArg-Gly-Asp-Mamb(5-(6-(6-hydrazinonicotina mido)hexanamide)))] was labeled with 99mTc using tricine and a series of imine-N-containing heterocycles as coligands. The imine-N-containing heterocycles include N-omega-Acetylhistamine (HIS-AC), N-(2-hydroxyethyl)isonicotinamide (ISONIC-HE), isonicotinic acid (ISONIC), isonicotinoyl-L-aspartic acid dimethyl ester (ISONIC-L-Asp-OMe2), 4-methyl-5-thiazoleethanol (MTE), nicotinic acid (NIC), 3-nitro-1,2,4-triazole (NTZ), 4-pyridylacetic acid (PA), 4-pyridineethanesulfonic acid (PES), and 3-pyridinesulfonic acid (PSA). The synthesis of these new ternary ligand [99mTc]HYNICtide complexes can be performed in one or two steps in high yield and high specific activity (>/=10 000 Ci/mmol HYNICtide). For example, the reaction of HYNICtide, [99mTc]pertechnetate, nicotinic acid, stannous chloride, and tricine at pH approximately 5 and 100 degreesC for 20 min results in the complex [99mTc(HYNICtide)(tricine)(NIC)] in >/=90% yield as determined by radio-HPLC. It was found that ternary ligand technetium complexes, [99mTc(HYNICtide)(tricine)(L)] (L = ISONIC, ISONIC-L-Asp-OMe2, ISONIC-HE, MTE, PA, PES, and PSA) are formed as equal mixtures of two isomeric forms. Complex [99mTc(HYNICtide)(tricine)(L)] (L = HIS-AC and NTZ) showed more than two well-resolved radiometric peaks at the retention times of interest, suggesting that they may have more than two forms in solution due to different bonding modalities of HIS-AC and NTZ. By a chirality experiment, it was found that the presence of two radiometric peaks is a result of the resolution of the two diastereomers which are formed by the combination of the chiral HYNICtide and the chiral technetium chelate. The formation of two diastereomers was also observed when a chiral imine-N-containing coligand was used for the radiolabeling of HYNIC-BA. The new ternary ligand [99mTc]HYNICtide complexes were found to be stable for up to 6 h in the reaction mixture. The high solution stability is attributed to their kinetic inertness. The composition of these complexes was determined to be 1:1:1:1 for Tc:HYNICtide:L:tricine (L = imine-N-containing heterocycles) through a series of mixed ligand experiments on the tracer (99mTc) level. The lipophilicity of the ternary ligand [99mTc]HYNICtide complexes can be systematically varied by the choice of polyaminocarboxylate and imine-N-containing coligands. Using the combination of tricine and an imine-N-containing coligand, HYNIC-derivatized peptides or other small molecules can be labeled with 99mTc in high specific activity and high stability for potential use as radiopharmaceuticals.     

A comparison of mass balance, pharmacokinetics and disposition of [14C(U)]- and [125I]recombinant human interleukin-2 in cynomolgus monkeys

Recombinant human interleukin-2 (rHuIL-2) has been metabolically labeled with 14C amino acids in Escherichia coli and affinity purified on a rHuIL-2 receptor affinity column. The radiolabeled molecule had a specific radioactivity of 238 dpm/unit and the identical amino acid sequence and biological activity as unlabeled rHuIL-2. In this study, we used this labeled [14C(U)]rHuIL-2 and commercially available [125I]rHuIL-2 (identical in sequence to the [14C(U)]rHuIL-2) to compare the mass balance, pharmacokinetics, and disposition in cynomolgus monkeys. After a single intravenous bolus dose of 4 x 10(5) units/kg, serum samples were collected for 7 days and examined for biological activity, total radioactivity, and by molecular size exclusion chromatography. Urine and feces were analyzed for total radioactivity. When analyzed for biological activity, both [14C(U)]- and [125I]rHuIL-2 exhibited the following pharmacokinetic parameters: terminal elimination half-life of 1-2 hr, AUC0-infinity ranged from 2005 to 4659 units x hr/ml, clearance was 90-200 ml/hr/kg, and volume of distribution ranged from 103 to 163 ml/kg. Comparison of the pharmacokinetic profiles of the two radiolabels were very different from bioactivity, in that the elimination half-lives for radioactivity were approximately 8 days and 10 hr for [14C(U)]- and [125I]rHuIL-2, respectively. We conclude that the [14C(U)]rHuIL-2 was metabolized to constituent amino acids and recycled into newly synthesized proteins from our size exclusion chromatography studies.(ABSTRACT TRUNCATED AT 250 WORDS)     

Estimation of unit risk for coke oven emissions

We are investigating the hypothesis that biotin multimers can be used with streptavidin and monoclonal antibody conjugates in cancer pretargeting protocols to provide a method of increasing the amount of radioactivity bound on cancer cells in patients. As part of that investigation, a series of biotinylated Starburst dendrimers (BSBDs) have been prepared and evaluated in vitro and in vivo. In this study, a new biotinidase-stabilized, water-solubilizing biotinylation reagent was prepared and reacted with Starburst (PAMAM) dendrimers, generations 0, 1, 2, 3, and 4. The reaction conditions employed resulted in perbiotinylation of generation 0 (four biotin moieties conjugated), generation 1 (eight biotin moieties conjugated), generation 2 (16 biotin moieties conjugated), and generation 3 (32 biotin moieties conjugated). With generation 4, incomplete biotinylation was achieved resulting in the largest portion of that BSBD having 51 biotin moieties (of 64 possible) conjugated. The ability of each BSBD to cross-link streptavidin (SAv) was examined in an in vitro assay. In that assay, an assessment was made of the quantity of [125I]SAv bound with polystyrene-bound SAv after treatment with the synthesized BSBDs. All BSBDs cross-linked the polystyrene-bound SAv with [125I]SAv; however, the amount of [125I]SAv bound varied with the different BSBDs. Roughly 1 equiv of [125I]SAv was bound when Starburst dendrimers containing three or four biotin moieties (generation 0) were used. Two equivalents were bound with BSBD generation 1, and 4 equiv were bound with BSBDs generations 2, 3, and 4. To assess the distribution of BSBDs generations 0, 1, and 2 in mice (at 4 h postinjection), a method was developed for radioiodinating them using the NHS ester of p-[125I]iodobenzoate ([125I]PIB). It was found that the radioiodinated BSBDs had low blood concentrations (i.e., 0.13-0.20% ID/g) at the 4 h time point. In fact, most tissues examined had low concentrations of biotinylated dendrimers, except kidney and liver. Kidney had the highest concentration of [125I]-labeled BSBDs, and its concentration increased with increasing size and charge of dendrimer (e.g., 8-48% ID/g). On the basis of the increased radioactivity observed in the in vitro assay and the rapid clearance from blood in mice, additional in vivo studies with perbiotinylated Starburst dendrimer, generation 2, are planned.     

Instability of pUC19 in Escherichia coli transcription termination factor mutant, rho026

We compared internalization of three radioiodinated octreotide (OCT) somatostatin (SS) analogs-[125I-Tyr3]OCT, [DTPA degrees, 125I-Tyr3]OCT, and [DOTA degrees,125I-Tyr3]OCT-by somatostatin receptor (SSR)-positive mouse AtT20 pituitary tumor cells and human insulinoma cells. The three SS analogs were internalized in a specific, time-dependent manner. Internalization was significantly inhibited by pertussis toxin (100 microg/l) by 38%, 43%, and 31%, and by an inhibitor of receptor-mediated endocytosis (phenyl arsine oxide; 10 microM) by 98%, 94%, and 92%, respectively. Binding affinities of the three radioligands were comparable (0.2, 0.2, and 0.3 nM, respectively). However, [DOTA degrees,125I-Tyr3]OCT was internalized in a five-fold higher amount in comparison with the two other radioligands. A comparably high uptake of [DOTA degrees, 125I-Tyr3]OCT was found in SSR-positive organs (pituitary, pancreas, and adrenals) in vivo in rats (a ten-fold, five-fold, and eight-fold higher uptake 4 hr post injection, respectively, compared with the two other radioligands). This resulted in very high target-background ratios for [DOTA degrees,125I-Tyr3]OCT 4 hr post injection amounting to 274, 566, and 623 in the pituitary, adrenals, and pancreas, respectively. Both in vivo and in vitro there was a rapid dissociation of radioactivity from the SSR-positive cells. Main conclusions are that: 1) coupling of chelating groups like DTPA or DOTA to the SS analog [Tyr3]OCT does not prevent the internalization of OCT after binding to SSRs; 2) [DOTA degrees, 125I-Tyr3]OCT is internalized in a significantly higher amount by AtT20 and human insulinoma cells and in vivo in rats in SSR-positive organs, in comparison with [DTPA degrees,125I-Tyr3]OCT and [125I-Tyr3]OCT; and 3) the very high target-background ratios in vivo make radioiodinated [DOTA degrees,Tyr3]OCT a very suitable ligand for SSR-targeted radioguided surgery of SSR-positive human neuroendocrine tumors.     

Proximal sciatic axotomy does not inhibit the induction of neurofilamentous inclusions following intracisternal aluminum chloride exposure

The present study evaluated 99mTc(V) DMSA as an agent for the visualization of inflammatory lesions in comparison to 99mTc(III) DMSA and 99mTC-HIG. All three radiopharmaceuticals were prepared with commercial kits. 99mTc(V) DMSA was prepared at neutral pH by the addition of first bicarbonate and then pertechnetate to the kit contents. The labeling efficiency was 99% as determined by ITLC. Abscesses were induced by i.m. injection of 50 microliters turpentine into the right thighs of 36 Swiss albino mice. Six days later 3.7 MBq of each radiopharmaceutical was i.v. administered to 12 mice. The mice were sacrificed at 1, 3, 6 and 24 h later. Scintigrams were obtained with a gamma camera. The abscesses were better visualized on scintigrams with 99mTc(V) DMSA compared to 99mTc(III) DMSA, starting at 1 h. The animals were dissected and the organs were removed, weighed and the radioactivity determined with a gamma counter. The abscess to other tissue ratios were higher with 99mTc(V) DMSA than the other radiopharmaceuticals. The max. abscess/muscle ratios were 9.46 +/- 3.20 (24 h), 4.19 +/- 1.39 (6 h) and 5.98 +/- 1.17 (24 h) and max. abscess/blood ratios were 6.22 +/- 1.41, 4.09 +/- 0.84 and 0.914 +/- 0.351 all at 24 h for 99mTc(V) DMSA, 99mTc(III) DMSA and 99mTc-HIG, respectively. Experimental arthritis was produced in New Zealand white rabbits by intra-articular injection of ovalbumin. Four days later 37 MBq of 99mTc(V) DMSA and 99mTc-HIG were each i.v. administered to 3 rabbits. Scintigrams obtained at 1, 3, 6, and 24 h clearly demonstrated arthritic joints. ROI's over arthritic joints were compared to contralateral normal joints (A/C). The max. A/C ratios were 2.10 +/- 0.31 (3 h) and 2.92 +/- 0.99 (24 h) for 99mTc(V) DMSA and 99mTc-HIG, respectively. Our results indicated the feasibility of imaging inflammatory lesions with 99mTc(V) DMSA.     

Comparison of metabolic and receptor imaging in recurrent medullary thyroid carcinoma with histopathological findings

Early diagnosis of metastases of medullary thyroid carcinoma (MTC) provides the optimal condition for curative outcome. The aim of this study was to appraise the detection of metastases in patients with recurrent MTC using [111In-DTPA-d-Phe1]-pentetreotide and pentavalent technetium-99m dimercaptosuccinic acid [99mTc(V)-DMSA] in comparison with histopathological findings. Eighteen MTC patients with persistently elevated tumour marker (calcitonin, carcinoembryonic antigen) levels underwent somatostatin receptor scintigraphy using [111In-DTPA-d-Phe1]-pentetreotide (222 MBq) with early (4 h after injection) and delayed (24 h) whole-body scans and single-photon emission tomography (SPET) imaging. Metabolic whole-body and SPET imaging using 500 MBq 99mTc(V)-DMSA was performed 4 h after injection. Metabolic and receptor imaging revealed 51 sites of focal accumulation in the 18 patients investigated. Comparison with histological findings revealed that metabolic and receptor imaging had a sensitivity of 84% for the diagnosis of MTC. Using [111In-DTPA-d-Phe1]-pentetreotide, SPET discovered four lymph node metastases in two patients in whom planar views had previously identified only one lymph node metastasis, and provided no new information in the other 16 patients. In comparison, SPET studies [using 99mTc(V)-DMSA] additionally localized eight lymph node metastases in four patients and confirmed the diagnosis of hepatic metastases (n=5) in another patient in whom conventional imaging modalities and planar views had previously detected only three liver metastases. Overall, lesion detection sensitivities for 99mTc(V)-DMSA and [111In-DTPA-D-Phe1]-pentetreotide were 69% and 29%, respectively. Five surgically removed foci were adjudged false-positive with respect to MTC metastases. False-positve results were caused by lymphadenitis, an enchondroma and a pheochromocytoma (histologically proven). The smallest lesion identified by metabolic imaging was a 6 mm in diameter lymph node metastasis located in the upper mediastinum. Somatostatin receptor scintigraphy only demonstrated tumour sizes more than 1 cm in diameter. These preliminary results suggest that the combination of metabolic [99mTc(V)-DMSA] and receptor ([111In-DTPA-D-Phe1]-pentetreotide) imaging is more sensitive for tumour localization in patients with recurrent MTC than the use of only one radiopharmaceutical. However, neither 99mTc(V)-DMSA nor [111In-DTPA-D-Phe1]-pentetreotide is specific for MTC and false-positive scintigraphic findings have to be considered. Furthermore, somatostatin receptor scintigraphy cannot visualize small tumour sites (<1 cm). Further studies are needed to evaluate the role of combined metabolic and receptor imaging in the management of patients with recurrent MTC.     

Fermentation of dietary fibre by human colonic bacteria: disappearance of, short-chain fatty acid production from, and potential water-holding capacity of, various substrates

beta-CIT (2 beta-carbomethoxy-3 beta-(4-iodophenyl)tropane) is a cocaine analogue with a high affinity for the dopamine transporter. [11C] beta-CIT was prepared by N-methylation of nor-beta-CIT with [11C]methyl iodide. The total radiochemical yield of [11C] beta-CIT was 40-50% with an overall synthesis time of 35-40 min. The radiochemical purity was > 99% and the specific radioactivity at the time of injection was about 1000 Ci/mmol (37 GBq/mumol). Autoradiographic examination of [11C] beta-CIT binding in human brains post-mortem demonstrated a high level of specific binding in the striatum. PET examination of [11C] beta-CIT in a Cynomolgus monkey showed a marked accumulation of radioactivity in the striatum. The ratio of radioactivity in the striatum-to-cerebellum approached 5 after 87 min. In a displacement experiment, radioactivity in the striatum but not in the cerebellum, was markedly reduced after injection of unlabelled cocaine. [11C] beta-CIT has a potential as ligand for PET examination of cocaine effects in man.     

Single photon emission computed tomography (SPECT) in a patient with bilateral temporal seizures: correlation between ictal EEG and postictal/ictal SPECT

We report a patient with bilateral independent temporal lobe seizures in whom two [99mTc]HMPAO single photon emission computed tomograph (SPECT) scans were performed during two different seizures. In the first periictal SPECT, [99mTc]HMPAO was injected in the interval between two closely spaced seizures (one localized in the left temporal lobe and the other in the right temporal lobe). SPECT images showed hypoperfusion in the left lateral temporal lobe, hyperperfusion of the left mesial temporal region, and pronounced hyperperfusion in the right anterior temporal lobe. These results suggest both a postictal left temporal SPECT pattern and an ictal right temporal pattern. In the second periictal SPECT, [99mTc]HMPAO was injected immediately after a right temporal lobe seizure and showed right lateral temporal lobe hypoperfusion and right mesial hyperperfusion, suggesting a postictal right temporal SPECT pattern. Interpretation of the periictal SPECT should take into account EEG changes at the time or in the minutes immediately after injection of [99mTc]HMPAO.     

Rapid uptake and binding of estradiol-17beta-6-(O-carboxymethyl)oxime:125I-labeled BSA by female rat liver

To investigate potential membrane-mediated responses to estrogen, a membrane-impermeant, radioiodinated, steroid-BSA conjugate--estradiol-17beta-6-(O-carboxymethyl)oxime:125I-labeled BSA (17beta-E-6-125I-BSA)--or related steroid conjugates, or 125I-BSA was injected into female Sprague-Dawley rats, and tissues were collected at varying times postinjection. The liver, adrenal, and spleen displayed the most prominent uptake of 17beta-E-6-125I-BSA, reaching a maximum of 43 times blood levels in sonicated liver samples at 5 min postinjection, but no uptake of 125I-BSA. Isolation of liver membranes by differential centrifugation showed that over 50% of recovered radioactivity was in association with microsomes and plasmalemma (P3 fraction) at 30 sec postinjection. By 60 min postinjection, over 75% of recovered radioactivity was in association with mitochondrial and lysosomal membranes (P2 fraction), and less than 10% remained in the P3 fraction. In vitro competition assays demonstrated two binding sites in liver P3 fractions. The spleen and liver also showed saturable binding in vivo. These data suggest the presence of at least one membrane-binding protein for estrogen in liver, adrenal, and spleen. Initial studies of affinity-purified liver P3 fractions using ligand blots indicated the presence of two binding proteins. These potential membrane estrogen-binding proteins may be involved in a very rapid shuttling of estrogen from the plasmalemma to mitochondria and lysosomes.     

18F]fluoroalkyl analogues of the potent 5-HT1A antagonist WAY 100635: radiosyntheses and in vivo evaluation

Two analogues of the potent 5-HT1A antagonist WAY 100635 have been synthesized and radiolabelled with 18F, namely N-[2-[4-(2-2'-[18F] fluoroethoxyphenyl)-1-piperazinyl]ethyl]-N-(2-pyridinyl)cyclohe xan e carboxamide ([18F]FEC) and N-[2-[4-(2-3'-[18F] fluoropropoxyphenyl)-1-piperazinyl]ethyl]-N-(2-pyridinyl)cycloh exa ne carboxamide ([18F]FPC). Biodistribution studies in rats showed selective uptake of both radiotracers in regions known to be rich in 5-HT1A receptors following i.v. injection. The ratio of radioactivity in hippocampus to that in the cerebellum was 5.5 (for [18F]FEC) and 7.5 (for [18F]FPC) at 60 min postinjection. Regional brain heterogeneity of radioactivity could be abolished by pretreatment with WAY 100635 and FPC but was unaffected by pretreatment with a variety of drugs including ketanserin, sulpiride, and SCH 23390. These results are compared vis-a-vis with those obtained using [11C]WAY 100635 to evaluate [18F]FEC and [18F]FPC as potential radiotracers for imaging 5-HT1A receptors by positron emission tomography.