Evaluation of tumor affinity of mono‐[123I]iodohypericin and mono‐[123I]iodoprotohypericin in a mouse model with a RIF‐1 tumor

In this study we have compared the tumour‐seeking properties of mono‐[¹²³I]iodoprotohypericin and mono‐[¹²³I]iodohypericin in C3H mice with a subcutaneous radiation‐induced fibrosarcoma‐1 tumor. After intravenous injection, both tracers were rapidly cleared from all organs and were retained by the tumors. There was no significant difference in tumor uptake of the two tracers at all studied time points (p > 0.05). To study the plausible mechanism of hypericin and mono‐iodohypericin uptake in tumor, their plasma binding profile was investigated. Both agents show high affinity for low‐density lipoproteins and to a lesser extent high‐density lipoproteins and other heavy proteins. Mono‐[¹²³I]iodohypericin appears to be more promising as a tumor diagnostic agent, given its faster clearance from all organs. Copyright © 2007 John Wiley & Sons, Ltd.     

L‐Amino acid load to enhance PET differentiation between tumor and inflammation: an in vitro study on 18F‐FET uptake

Labeled amino acids (AA) are tumor tracers for use in nuclear medecine. O‐(2‐[¹⁸F]fluoroethyl)‐L ‐tyrosine (FET) is transported by the L ‐system, known to function as an exchanger. In vitro utilization of FET, after a preload or prior to an afterload of non radioactive L ‐amino acids, was evaluated in order to measure the potential effects of AA content on the distinction between tumor and inflammatory lesions. Cellular uptake of FET was studied on rat osteosarcoma cells (ROS 17/2.8) and human leukocytes, initially loaded with nonradioactive L ‐tyrosine or L ‐methionine. FET efflux was evaluated from cells loaded with nonradioactive L ‐phenylalanine after tracer uptake. ROS 17/2.8 showed a higher sensitivity to preload and afterload effects on cellular FET content as compared with the leukocytes. We conclude that preload with L ‐tyrosine, prior to the administration of FET, may be a potential procedure to improve PET differentiation between tumor and inflammatory lesions. Copyright © 2006 John Wiley & Sons, Ltd.     

In vivo evaluation of the dopaminergic neurotransmission system using [123I]FP‐CIT SPECT in 6‐OHDA lesioned rats

The 6‐hydroxydopamine (6‐OHDA) rodent model of Parkinson's disease (PD) has been used to evaluate the nigrostriatal pathway. The aim of this work was to explore the relationship between the degree of 6‐OHDA‐induced dopaminergic degeneration and [¹²³I]FP‐CIT binding using single photon emission computed tomography (SPECT). Fourteen rats received a 6‐OHDA injection (4 or 8 µg) into the left medial forebrain bundle. After 3 weeks, magnetic resonance imaging and scans with a small‐animal SPECT system were performed. Finally, the nigrostriatal lesion was assessed by immunohistochemical analysis. Immunohistochemical analysis confirmed two levels of dopaminergic degeneration. Lesions induced by 6‐OHDA diminished the ipsilateral [¹²³I]FP‐CIT binding by 61 and 76%, respectively. The decrease in tracer uptake between control and lesioned animals was statistically significant, as was the difference between the two 6‐OHDA lesioned groups. Results concluded that [¹²³I]FP‐CIT SPECT is a useful technique to discriminate the degree of dopaminergic degeneration in a rat model of PD. Copyright © 2014 John Wiley & Sons, Ltd.     

Simultaneous [99mTc]TRODAT-1 and [123I]ADAM Brain SPECT in Nonhuman Primates

Purpose  This study examined the feasibility of simultaneous dopamine and serotonin transporter imaging using [¹²³I]ADAM and [^99mTc]TRODAT-1 single photon emission computed tomography (SPECT). Procedures  Simultaneous [¹²³I]ADAM (185 MBq) and [^99mTc]TRODAT-1 (740 MBq) SPECT was performed in three age-matched female Formosan rock monkeys. An asymmetric energy window was used for dual, and symmetric energy windows were used for single-isotope imaging. Oral fluoxetine (20 mg) and intravenous methylphenidate HCl (1 mg/kg) were given 24 h and 10 min, respectively, before dual-isotope SPECT to test imaging specificities of [¹²³I]ADAM and [^99mTc]TRODAT-1. Results  Comparable image quality and uptake ratios between dual- and single-isotope SPECT scans were found. Dual-isotope SPECT in fluoxetine-pretreated monkeys showed decreased uptake of [¹²³I]-ADAM, but not of [^99mTc]TRODAT-1. Dual-isotope SPECT in methylphenidate-pretreated monkeys showed decreased [^99mTc]TRODAT-1 uptake without affecting [¹²³I]-ADAM uptake. Conclusion  Simultaneous [¹²³I]-ADAM and [^99mTc]TRODAT-1 SPECT appears promising in nonhuman primates and may provide a suitable preclinical model with further clinical implications.     

Spatial Inhomogeneity of Cardiac Norepinephrine Transport Protein and Meta-[123I]Iodobenzylguanidine Uptake in Swine Myocardial Tissue

Purpose

The aim of the present study was to evaluate the expression of the cardiac norepinephrine transporter (NET) in the left ventricle (LV) of healthy pigs and its relationship with regional meta-[¹²³I]iodobenzylguanidine ([¹²³I]MIBG) myocardial uptake.

Procedures

Experiments were performed on animals injected with [¹²³I]MIBG and acquired 2 h later using an ultrafast CZT gamma camera to assess the regional myocardial uptake. After image acquisition, animals were euthanized; the heart was quickly excised and underwent to an ex vivo single photon emission tomography (SPECT) imaging. Four small samples of tissue were then harvested from mid-walls and apex of the left ventricle; NET densities were evaluated and further normalized for protein loading per cardiac region.

Results

Three variants of NET protein with different molecular weights were detected. The expression of NET was not homogenous in the LV, with the highest density in the inferior wall and the lowest one in the apical area. The regional in vivo [¹²³I]MIBG uptake revealed an analogous trend, showing a good linear relationship with NET expression. Parallel results were obtained from the ex vivo study.

Conclusion

This study elucidates the expression of three different variants of NET proteins into the left ventricular myocardium of a healthy pig. NET expression into the LV was not homogeneous and paralleled by differences in regional [¹²³I]MIBG uptake. Moreover, the correlation and the agreement between measurements of regional expression of NET variants and [¹²³I]MIBG uptake represent a relevant finding for inferences about NET expression in the context of clinical imaging.

     

Effect of chronic intra‐peritoneally administered chimeric peptide of met‐enkephalin and FMRFa‐[d‐Ala2]YFa‐on antinociception and opioid receptor regulation

The physiological role of NPFF/FMRFa family of peptides is complex and exact mechanism of action of these peptides is not yet completely understood. In same line of scrutiny, previously we reported an enzymatically stable chimeric analog of YGGFMKKKFMRFamide (YFa) i.e., [d ‐Ala²]YAGFMKKKFMRFamide ([d ‐Ala²]YFa) which have a role in antinociception and modulatory effect on opioid analgesia. In continuation, presently we investigated using tail‐flick test whether [d ‐Ala²]YFa on systemic administration induced any antinociception in rats and if so then which specific opioid receptor(s) μ, δ or κ mediated it. Further, the antinociceptive effect of [d ‐Ala²]YFa on 6 days chronic intra‐peritoneal (i.p.) treatment in rats was examined and finally, effect of this chronic treatment on the differential expression of opioid receptors was assessed. [d ‐Ala²]YFa on i.p. administration induced dose dependent antinociception which was mainly mediated by δ (DOR) and partially by μ (MOR) and κ (KOR) opioid receptors. Moreover, its antinociceptive effect remained comparable throughout the chronic treatment even during insufficient availability of DOR1. Importantly, during this treatment the mRNA expression of all three opioid receptors (MOR1, KOR1 and DOR1) was increased as assessed by real‐time RTPCR though subsequent western blot analysis revealed a selective increase in the protein level of DOR1, only. Thus, pharmacological behavior of [d ‐Ala²]YFa suggests that competency of an opioid agonist to bind with multiple opioid receptors may enhance its potency to induce tolerance free analgesia.     

Evaluation of [123I]IBZM pinhole SPECT for the detection of striatal dopamine D2 receptor availability in rats

Single photon emission computed tomography (SPECT) and MRI coregistration have been assessed to characterize striatal dopamine D2/D3 receptor (D2/D3R) availability in rats following injection of the D2 and D3R radioligand [123I] iodobenzamide ([123I]IBZM). High-resolution SPECT data were obtained with a pinhole collimator. In order to precisely estimate brain regions of low radioligand uptake, SPECT images were coregistered onto a MRI template with high accuracy (maximum mismatch 1.1 mm). To evaluate an adequate dose of radioligand to be administered without exceeding the radioligand-to-receptor occupancy >5% and to define an appropriate time period for image acquisition, three untreated groups of animals received 29.6, 37, and 44.4 MBq of [123I]IBZM and underwent five consecutive SPECT acquisitions lasting 64 min each. Ratio calculations between specific striatal radioligand uptake and nondisplaceable cerebellar uptake revealed a secular equilibrium between 75 and 355 min post-tracer application in all three animal groups. Consequently, since the highest regional uptake values were obtained in the animal group receiving 44.4 MBq [123I]IBZM, this injection dose was considered to be appropriate. Finally, the capacity of the imaging method to detect distinct severity levels of striatal dopamine D2/D3 receptor loss was tested in a low, medium, and high dose quinolinic acid (QA) animal model of Huntington's disease. Motor impairment indicative of striatal dysfunction was monitored using amphetamine-induced rotational behavior and locomotor activity. Loss of striatal D2/D3R bearing medium-sized spiny neurons was assessed by DARPP-32 immunohistochemistry and compared to [123I]IBZM binding. Optical density measures of DARPP-32 immunohistochemistry demonstrated QA dose-dependent mild to subtotal unilateral striatal lesions ranging from 29.4% to 96.9% when compared to the nonlesioned side. Linear regression analysis showed that measurements of striatal DARPP-32 optical density and striatal [123I]IBZM uptake of the lesioned side were highly correlated (r2=0.83; P<0.001) whereas correlation with locomotor activity was less tight (r2=0.23; P<0.05; amphetamine-induced rotational behavior was not significantly correlated). This is the first study to demonstrate that in vivo [123I]IBZM SPECT and MRI coregistration are highly sensitive and, in contrast to behavioral measures, accurately detect mild to subtotal striatal lesions by measuring loss of D2/D3R availability. SPECT-MRI-based estimation of regional [123I]IBZM uptake provides a cost effective and widely available in vivo imaging technique for assessing striatal integrity in animal studies.     

123I‐MIBG imaging for detection of anthracycline‐induced cardiomyopathy

Due to improvements in early detection and treatment of malignant disease, the population of cancer survivors is constantly expanding. Cancer survivors are faced with chemotherapy‐related long‐term side effects, including irreversible cardiac injury with risk of heart failure (HF). Numerous antineoplastic regimens are associated with risk of cardiac side effects, but anthracyclines in particular carry a severe risk of cardiotoxicity. Currently, serial echocardiographic evaluation of resting left ventricular ejection fraction (LVEF) is the gold standard for monitoring anthracycline‐induced cardiac side effects from chemotherapy. LVEF measurements are, however, limited by their low sensitivity. A normal LVEF does not exclude cardiotoxicity and declines in LVEF are usually not observed before the occurrence of irreversible cardiomyopathy. Hence, a clinically applicable high‐sensitivity diagnostic tool for early detection of chemotherapy‐related cardiotoxicity is still lacking and alternative non‐invasive imaging modalities are therefore being investigated. ¹²³I‐MIBG is a noradrenaline (NA) analogue used for evaluation of cardiac adrenergic function, including assessment of HF prognosis and evaluation of HF treatment response. However, the role of ¹²³I‐MIBG for monitoring chemotherapy‐related cardiotoxicity is still unclear. Here, we review the value of ¹²³I‐MIBG imaging for early detection and prevention of anthracycline‐induced cardiomyopathy.     

Preclinical evaluation of [111In]MICA‐401, an activity‐based probe for SPECT imaging of in vivo uPA activity

Urokinase‐type plasminogen activator (uPA) and its inhibitor PAI‐1 are key players in cancer invasion and metastasis. Both uPA and PAI‐1 have been described as prognostic biomarkers; however, non‐invasive methods measuring uPA activity are lacking. We developed an indium‐111 (¹¹¹In)‐labelled activity‐based probe to image uPA activity in vivo by single photon emission computed tomography (SPECT). A DOTA‐conjugated uPA inhibitor was synthesized and radiolabelled with ¹¹¹In ([¹¹¹In]MICA‐401), together with its inactive, hydrolysed form ([¹¹¹In]MICA‐402). A biodistribution study was performed in mice (healthy and tumour‐bearing), and tumour‐targeting properties were evaluated in two different cancer xenografts (MDA‐MB‐231 and HT29) with respectively high and low levels of uPA expression in vitro, with either the active or hydrolysed radiotracer. MicroSPECT was performed 95 h post injection followed by ex vivo biodistribution. Tumour uptake was correlated with human and murine uPA expression determined by ELISA and immunohistochemistry (IHC). Biodistribution data with the hydrolysed probe [¹¹¹In]MICA‐402 showed almost complete clearance 95 h post injection. The ex vivo biodistribution and SPECT data with [¹¹¹In]MICA‐401 demonstrated similar tumour uptakes in the two models: ex vivo 5.68 ± 1.41%ID/g versus 5.43 ± 1.29%ID/g and in vivo 4.33 ± 0.80 versus 4.86 ± 1.18 for MDA‐MB‐231 and HT‐29 respectively. Human uPA ELISA and IHC showed significantly higher uPA expression in the MDA‐MB‐231 tumours, while mouse uPA staining revealed similar staining intensities of the two tumours. Our data demonstrate non‐invasive imaging of uPA activity in vivo, although the moderate tumour uptake and hence potential clinical translation of the radiotracer warrants further investigation. Copyright © 2016 John Wiley & Sons, Ltd.     

Biodistribution and evaluation of 131I‐labeled neuropilin‐binding peptide for targeted tumor imaging

Neuropilin‐1 (NRP‐1) is overexpressed in several kinds of cancer cell and contributes to tumor aggressiveness. Recently, the arginine/lysine‐rich peptide with C‐terminal motifs (R/K)XX(R/K) indicated promising penetrating and transporting capability into NRP‐1 positive cancer cells. In the present study, we describe a ¹³¹I‐labeled C‐end rule motif peptide conjugate, Tyr–tLyp‐1, for NRP‐1 positive tumor targeting and imaging properties. Briefly, a truncated Lyp‐1 peptide was designed to expose its C‐end motif and conjugated to tyrosine for radiolabeling after structural modification. The peptide indicated specific binding to A549 cancer cells at 2 μM concentration, and its binding was dependent on NRP‐1 expression and could be inhibited by other NRP‐1‐binding peptides. In vivo imaging of ¹³¹I‐labeled Tyr–tLyp‐1peptide showed that a subcutaneous A549 xenograft tumor could be visualized using a SPECT/CT scanner. The tumor uptake of ¹³¹I‐Tyr–tLyp‐1 was 4.77 times higher than the uptake in muscles by SPECT/CT software quantification at 6 h post injection. Together, this study indicated that truncated Lyp‐1 peptide could specifically localize in NRP‐1 positive tumors and successfully mediate the ¹³¹I radionuclide diagnosis, indicating promising targeted imaging capability for NRP‐1 positive tumors. Copyright © 2016 John Wiley & Sons, Ltd.     

Syntheses and preliminary evaluation of [18F]AlF‐NOTA‐G‐TMTP1 for PET imaging of high aggressive hepatocellular carcinoma

The goal of this study is to evaluate a new ¹⁸F‐labeled imaging agent for diagnosing high metastatic (aggressive) hepatocellular carcinoma using positron emission tomography (PET). The new ¹⁸F‐labeled imaging agent [¹⁸F]AlF‐NOTA‐G‐TMTP1 was synthesized and radiolabeled with ¹⁸F using NOTA‐AlF chelation method. The tumor‐targeting characteristics of [¹⁸F]AlF‐NOTA‐G‐TMTP1 was assessed in HepG2, SMCC‐7721, HCC97L and HCCLM3 xenografts. The total synthesis time was about 20 min with radiochemical yield of 25 ± 6%. The specific activity was about 11.1–14.8 GBq/µmol at the end of synthesis based on the amount of peptide used and the amount of radioactivity trapped on the C₁₈ column. The log P value of [¹⁸F]AlF‐NOTA‐G‐TMTP1 was ‐3.166 ± 0.022. [¹⁸F]AlF‐NOTA‐G‐TMTP1 accumulated in SMCC‐7721 and HCCLM3 tumors (high metastatic potential) in vivo and result in tumor/muscle (T/M) ratios of 4.5 ± 0.3 and 4.7 ± 0.2 (n = 4) as measured by PET at 40 min post‐injection (p.i.). Meanwhile, the tumor/muscle (T/M) ratios of HepG2 and HCC97L tumors (low metastatic potential) were1.6 ± 0.3 and 1.8 ± 0.4. The tumor uptake of [¹⁸F]AlF‐NOTA‐G‐TMTP1 could be inhibited 61.9% and 57.6% by unlabeled G‐TMTP1 in SMCC‐7721 and HCCLM3 xenografts at 40 min p.i., respectively. Furthermore, [¹⁸F]AlF‐NOTA‐G‐TMTP1 showed pretty low activity in the liver and intestines in all tumor bearing mice, such in vivo distribution pattern would be advantageous for the detection of hepatic carcinoma. Overall, [¹⁸F]AlF‐NOTA‐G‐TMTP1 may specifically target high metastatic or/and aggressive hepatocellular carcinoma with low background activity and, therefore, holds the potential to be used as an imaging agent for detecting tumor lesions within the liver area. Copyright © 2016 John Wiley & Sons, Ltd.     

Molecular recognition of sugars by lanthanide (III) complexes of a conjugate of N,N‐bis[2‐[bis[2‐(1, 1‐dimethylethoxy)‐2‐oxoethyl]amino]ethyl]glycine and phenylboronic acid

A novel conjugate of phenylboronic acid and an Ln(DTPA) derivative, in which the central acetate pendant arm was replaced by the methylamide of L ‐lysine, was synthesized and characterized. The results of a fit of variable ¹⁷O NMR data and a ¹H NMRD profile show that the water residence lifetime of the Gd(III) complex (150 ns) is shorter than that of the parent compound Gd(DTPA)^2? (303 ns). Furthermore, the data suggest that several water molecules in the second coordination sphere of Gd(III) contribute to the relaxivity of the conjugate. The Ln(III) complexes of this conjugate are highly suitable for molecular recognition of sugars. The interaction with various sugars was investigated by ¹¹B NMR spectroscopy. Thanks to the thiourea function that links the phenylboronic acid targeting vector with the DTPA derivative, the interactions are stronger than that of phenylboronic acid itself. In particular, the interaction with N‐propylfructosamine, a model for the glucose residue in glycated human serum albumin (HSA), is very strong. Unfortunately, the complex also shows a rather strong interaction with hexose‐free HSA (K_A = 705 ± 300). Copyright © 2007 John Wiley & Sons, Ltd.     

Synthesis and evaluation of 3′-[18F]fluorothymidine-5′-squaryl as a bioisostere of 3′-[18F]fluorothymidine-5′-monophosphate

The squaryl moiety has emerged as an important phosphate bioisostere with reportedly greater cell permeability. It has been used in the synthesis of several therapeutic drug molecules including nucleoside and nucleotide analogues but is yet to be evaluated in the context of positron emission tomography (PET) imaging. We have designed, synthesised and evaluated 3′-[¹⁸F]fluorothymidine-5′-squaryl ([¹⁸F]SqFLT) as a bioisostere to 3′-[¹⁸F]fluorothymidine-5′-monophosphate ([¹⁸F]FLTMP) for imaging thymidylate kinase (TMPK) activity. The overall radiochemical yield (RCY) was 6.7 ± 2.5% and radiochemical purity (RCP) was >90%. Biological evaluation in vitro showed low tracer uptake (<0.3% ID mg⁻¹) but significantly discriminated between wildtype HCT116 and CRISPR/Cas9 generated TMPK knockdown HCT116^shTMPK−. Evaluation of [¹⁸F]SqFLT in HCT116 and HCT116^shTMPK− xenograft mouse models showed statistically significant differences in tumour uptake, but lacked an effective tissue retention mechanism, making the radiotracer in its current form unsuitable for PET imaging of proliferation.

[¹⁸F]SqFLT was developed to bypass thymidine kinase 1 (TK1) and evaluated for PET imaging of DNA synthesis.     

The effect of glutamine on protein balance and amino acid flux across arm and leg tissues in healthy volunteers

Background. Glutamine is important in nitrogen transportation and the physiological control of acid–base regulation. In addition, it has been assumed that glutamine regulates protein balance in skeletal muscles based on findings in both experimental and clinical studies. However, little information on glutamine and its effect on protein dynamics in normal individuals is available. Therefore, the aim of this study was to evaluate whether glutamine improves protein balance and uptake of various indispensable amino acids across peripheral tissue in healthy individuals. Material and methods. Standard primed constant infusions of L ‐[ring‐²H₅]phenylalanine and [ring 3,3‐²H₂]tyrosine (2 μmol kg^?1 h^?1) were performed after overnight fast in five healthy male volunteers before and during infusions of a standard and a glutamine/tyrosine enriched amino acid solution. Flux measurements of amino acids (AA) including 3‐methylhistidine, glucose, lactate and free fatty acids (FFA) were performed across arm and leg tissues. Results. Infusion of the standard AA solution (0·2 g N kg^?1 day^?1) increased the net uptake of individual amino acids, but provision of the enriched solution (0·4 g N kg^?1 day^?1) with increased amounts of glutamine and tyrosine seemed to compete unfavourably with the net uptake of other key amino acids as methionine and phenylalanine, which are indispensable in muscles for protein synthesis. Increased flux of amino acids across peripheral tissues did not influence on flux of glucose, free fatty acid and lactate. Conclusions. Glutamine provision did neither stimulate protein synthesis nor attenuate breakdown of either globular or myofibrillar proteins in skeletal muscles of healthy volunteers.     

[68Ga]‐HP‐DO3A‐nitroimidazole: a promising agent for PET detection of tumor hypoxia

The goal of this study is to evaluate a new ⁶⁸Ga‐based imaging agent for detecting tumor hypoxia using positron emission tomography (PET). The new hypoxia targeting agent reported here, [⁶⁸Ga]‐HP‐DO3A‐nitroimidazole ([⁶⁸Ga]‐HP‐DO3A‐NI), was constructed by linking a nitroimidazole moiety with the macrocyclic ligand component of ProHance®, HP‐DO3A. The hypoxia targeting capability of this agent was evaluated in A549 lung cancer cells in vitro and in SCID mice bearing subcutaneous A549 tumor xenografts. The cellular uptake assays showed that significantly more [⁶⁸Ga]‐HP‐DO3A‐NI accumulates in hypoxic tumor cells at 30, 60 and 120 min than in the same cells exposed to 21% O₂. The agent also accumulated in hypoxic tumors in vivo to give a tumor/muscle ratio (T/M) of 5.0 ± 1.2 (n = 3) as measured by PET at 2 h post‐injection (p.i.). This was further confirmed by ex vivo biodistribution data. In addition, [⁶⁸Ga]‐HP‐DO3A‐NI displayed very favorable pharmacokinetic properties, as it was cleared largely through the kidneys with little to no accumulation in liver, heart or lung (%ID/g < 0.5%) at 2 h p.i. The specificity of the agent for hypoxic tissues was further validated in a comparative study with a control compound, [⁶⁸Ga]‐HP‐DO3A, which lacks the nitroimidazole moiety, and by PET imaging of tumor‐bearing mice breathing air versus 100% O₂. Given the commercial availability of cGMP ⁶⁸Ge/⁶⁸Ga generators and the ease of ⁶⁸Ga labeling, the new agent could potentially be widely applied for imaging tumor hypoxia prior to radiation therapy. Copyright © 2015 John Wiley & Sons, Ltd.     

Non‐competitive interaction between raclopride and spiperone on human D2L‐receptors in intact Chinese hamster ovary cells

We recently investigated the binding properties of the antagonists [³H]‐raclopride and [³H]‐spiperone to intact Chinese hamster ovary cells expressing recombinant human D_2long‐dopamine receptors (CHO‐D_2L cells). Compared with saturation binding with [³H]‐raclopride, raclopride reduced [³H]‐spiperone binding with to low potency in competition binding experiments. The present findings illustrate the ability of spiperone to inhibit [³H]‐raclopride binding non‐competitively. While raclopride only decreases the apparent K_D of [³H]‐raclopride in saturation binding experiments, spiperone only decreases the number of sites to which [³H]‐raclopride binds with high affinity. Also, while the IC₅₀ of raclopride depends on the concentration of [³H]‐raclopride in competition experiments, this is not the case for spiperone. Kinetic studies reveal that the binding of raclopride at its high affinity sites does not affect the association of subsequently added [³H]‐spiperone nor the rebinding of freshly dissociated [³H]‐spiperone to the same or surrounding receptors. Yet, spiperone does not affect the dissociation rate of [³H]‐raclopride and raclopride does not affect the (genuine) dissociation rate of [³H]‐spiperone. The easiest way to interpret the present findings in molecular terms is to assume that D_2L‐receptors or their dimeric complexes possess two distinct binding sites: one with high affinity/accessibility for [³H]‐raclopride and the other one with high affinity/accessibility for [³H]‐spiperone. The ability of bound spiperone to inhibit high affinity raclopride binding while the reverse is not the case suggests for the occurrence of non‐reciprocal allosteric interactions. These new findings could point at the occurrence of allosteric interactions between different classes of D₂‐receptor antagonists.     

Detection of preclinical Parkinson disease in at-risk family members with use of [123I]beta-CIT and SPECT: an exploratory study.

OBJECTIVE: To explore whether the radioligand 2 beta-carboxymethoxy-3 beta-(4-[123I] iodophenyl) tropane ([123I]beta-CIT) and single-photon emission computed tomography (SPECT) can detect decreased striatal uptake in at-risk relatives of patients with Parkinson disease (PD). PATIENTS AND METHODS: Ten PD patients, 10 at-risk first-degree relatives of PD patients, and 10 controls underwent [123I]beta-CIT and SPECT brain imaging. Their striatal uptake ratios were compared. RESULTS: Age-adjusted specific to nonspecific striatal uptake ratios were lower in patients compared with controls and with relatives; however, ratios were similar in relatives and controls. Among relatives, ratios were consistently lower in subgroups postulated to be at higher risk for preclinical PD. CONCLUSION: Our findings provide preliminary support that [123I]beta-CIT and SPECT may detect decreased striatal uptake in relatives of PD patients postulated to be at higher risk for PD.     

Biodistribution of [<Superscript>68</Superscript>Ga]PSMA-HBED-CC in Patients with Prostate Cancer: Characterization of Uptake in Normal Organs and Tumour Lesions

Purpose

The aim of this study was to determine the physiological and pathophysiological biodistribution of [⁶⁸Ga]PSMA-HBED-CC (PSMA-11) ([⁶⁸Ga]PSMA) in patients with prostate cancer (PCA) to establish the range of normal uptake in relevant organs and primary prostate tumours, locally recurrent PCA, lymph and bone metastases and other metastatic lesions. Additionally, we aimed to determine a cut-off uptake value for differentiation of primary tumours from normal prostate tissue.

Procedures

Overall, [⁶⁸Ga]PSMA positron emission tomography/x-ray computed tomography (PET/CT) of 101 patients (mean age 69.1 years) with PCA was analysed retrospectively. For assessment of tracer biodistribution, maximum standardized uptake values (SUVmax) were calculated for various normal organs, as well as for primary tumours (PT) and/or metastases. Results are presented as median, interquartile range (IQR; 25th quantil–75th quantil) and range (minimum–maximum).

Results

[⁶⁸Ga]PSMA PET/CT was performed 50 min (range 30–126) after injection of 109 MBq (range 84–158). Regarding biodistribution, highest uptake (median/IQR/range) of the tracer was found in the kidneys (49.6/40.7–57.6/2.7–97.0) followed by the submandibular glands (17.3/13.7–21.2/7.5–30.4), parotid glands (16.1/12.2–19.8/5.5–30.9) and duodenum (13.8/10.5–17.2/5.8–26.9). The best cut-off value for differentiating physiological uptake in the primary tumour from that in the prostate was found to be an SUVmax of 3.2. The median SUVmax in the PT (n?=?35), locally recurrent PCA (n?=?8), lymph node (n?=?166), bone (n?=?157) and other metastases (n?=?3) were 10.2, 5.9, 6.2, 7.4 and 3.8, respectively. The best cut-off values for differentiating non-pathological uptake in lymph nodes and bones from tumour uptake were found to be SUVmax of 3.2 and 1.9, respectively. Patients with PSA <2 had significantly lower SUVmax in bone metastases as compared to patients with PSA ≥2 (p?<?0.01).

Conclusions

This biodistribution study provided a broad range of uptake data of [⁶⁸Ga]PSMA-11 for normal organs/tissues, primary prostate tumours and metastatic lesions based on a large patient cohort. Both PT and small metastatic lesions were detectable due to their high tracer uptake. Four-times-higher median uptake in PT in comparison to normal prostate stroma resulted in a high diagnostic accuracy that could potentially be used for multimodal image-guided biopsy with dedicated reconstruction software.

     

Poly(amino acid)‐based fibrous scaffolds modified with surface‐pendant peptides for cartilage tissue engineering

In this study, fibrous scaffolds based on poly(γ‐benzyl‐l ‐glutamate) (PBLG) were investigated in terms of the chondrogenic differentiation potential of human tooth germ stem cells (HTGSCs). Through the solution‐assisted bonding of the fibres, fully connected scaffolds with pore sizes in the range 20–400 µm were prepared. Biomimetic modification of the PBLG scaffolds was achieved by a two‐step reaction procedure: first, aminolysis of the PBLG fibres’ surface layers was performed, which resulted in an increase in the hydrophilicity of the fibrous scaffolds after the introduction of N⁵‐hydroxyethyl‐l ‐glutamine units; and second, modification with the short peptide sequence azidopentanoyl–GGGRGDSGGGY–NH₂, using the 'click' reaction on the previously modified scaffold with 2‐propynyl side‐chains, was performed. Radio‐assay of the ¹²⁵I‐labelled peptide was used to evaluate the RGD density in the fibrous scaffolds (which varied in the range 10^–3–10 pm /cm²). All the PBLG scaffolds, especially with density 90 ± 20 fm /cm² and 200 ± 100 fm /cm² RGD, were found to be potentially suitable for growth and chondrogenic differentiation of HTGSCs. Copyright © 2015 John Wiley & Sons, Ltd.