A new technique for radiolabelling of humic substances

A new method of radiolabelling of humic substances (HS) in the aqueous phase has been developed. Radiolabelling with the short-lived positron-emitter18F was carried outviadiazonium coupling to electron-rich aromatic residues of the humic substances. Labelling yields of up to 75% were obtained after optimization of the synthetic procedure. Introductory experimental steps were performed for testing the labelling stability of the humic substances with ultrafiltration, electrophoretic and chromatographic methods.

[Successful open vascular-surgical supracoeliac anastomosis of a bifurcational prosthesis with simultaneous prosthetomesenteric and renal revascularisation in Leriche's syndrome with high occlusion]

BACKGROUND

Based on an extraordinary case -report on a patient with almost symptomless supramesenteric occlusion of the aorta, the successful management and favourable outcome including almost normalised renal function (in addition to appropriate diagnostic and operative tactics) achieved by a technically challenging vascular-surgical intervention and subsequent intensive medical and nephrological care are described.

RESULTS

In a 49-year-old male patient, a "high" aortic occlusion just below the branching of the coeliac trunk with arterial perfusion of the abdomen and the lower extremities via arterial collaterals from the 4 (th) to 6 (th) intercostal arteries was diagnosed. Both renal arteries were occluded leading to a consecutive renal insufficiency with need for dialysis and renovascularly induced hypertension. However, a residual perfusion of the parenchyma of the left kidney was detectable. Therapeutic measures comprised, after haemodialysis with accompanying antihypertensive medication, open supracoeliac aortobifemoral implantation of a prosthesis, revascularisation of the left renal artery (prosthetic bypass) and prostheticomesenteric bypass implantation. Postoperatively, a reestablished renal perfusion was observed in spite of the preoperatively prolonged lack of appropriate arterial perfusion (last dialysis, 11 (th) POD / discharge, 18 (th) POD). At 3 months postoperatively, the patient reported an increase of his body weight of 8 kg (at 6 months, 20 kg; improved but still elevated laboratory parameters indicating renal insufficiency; RR within normal range). Postinterventional MR angiography revealed a regular perfusion of the bifurcational prosthesis and of the bypasses to the superior mesenteric and left renal arteries.

CONCLUSION

This exemplary case demonstrates impressively the individual therapeutic chances, options and the potential in the diagnostic and therapeutic interdisciplinary management and its combined expertise. The clinical course in this case indicates that the assessment of the arterial blood supply has to be included in the diagnostic of an acute renal insufficiency associated with anuria. If there is a minimal residual perfusion, which might just be sufficient for maintenance of structural integrity, there is a real chance for a restitution of renal function after successful revascularisation.

Norchloro-fluoro-homoepibatidine (NCFHEB) - a promising radioligand for neuroimaging nicotinic acetylcholine receptors with PET

Cholinergic neurotransmission depends on the integrity of nicotinic acetylcholine receptors (nAChRs), and impairment of both is characteristic for various neurodegenerative diseases. Visualization of specific receptor subtypes by positron emission tomography (PET) has potential to assist with diagnosis of such neurodegenerative diseases and with design of suitable therapeutic approaches. The goal of our study was to evaluate in vivo the potential of (18)F-labelled (+)- and (-)-norchloro-fluoro-homoepibatidine ([(18)F]NCFHEB) in comparison to 2-[(18)F]F-A-85380 as PET tracers. In the brains of NMRI mice, highest levels of radioactivity were detected at 20 min post-injection of (+)-[(18)F]NCFHEB, (-)-[(18)F]NCFHEB, and 2-F-[(18)F]-A-85380 (7.45, 5.60, and 3.2% ID/g tissue, respectively). No marked pharmacological adverse effects were observed at 25 mug NCFHEB/kg. Uptake studies in RBE4 cells and in situ perfusion studies suggest an interaction of epibatidine and NCFHEB with the carrier-mediated choline transport at the blood-brain barrier. The data indicate that (+)- and (-)-[(18)F]NCFHEB have potential for further development as PET tracers.

Factors affecting the specific activity of [18F]fluoride from a [18O]water target

AIM

Characterisation of the influence of different polymeric tube materials of a water target system, used for the production of 18F activity, on the specific activity of radiotracers.

MATERIAL, METHODS

Target water samples taken from different locations of the 18F water target system of a Cyclone 18/9 cyclotron, equipped with Teflon (PTFE) or polypropylene (PP) tubes, were analyzed for non-radioactive [19F]fluoride content. [19F]Fluoride content was measured by ion chromatography (IC20, Dinoex) with suppressed conductivity detection. Both the ion chromatographic results and the amount of 18F activity produced were used for the calculation of the specific activity (SA) of [18F]fluoride at the start of the labelling synthesis. To check these results, the SA of the labelled receptor ligand [18F]ZK811460 was also determined by using the different tubing materials.

RESULTS

Dose-exposed PTFE tubes of the target dispensing (loading) system were identified to be a major source of [19F]fluoride contamination.

CONCLUSION

By replacing PTFE tubes of the target dispensing system with PP tubes, the content of 19F was reduced considerably resulting in an increase of SA of the radiotracer [18F]ZK811460 by factor of two.

[1-(11)C]acetate uptake is not increased in renal cell carcinoma

PURPOSE

The purpose of this study was to investigate the potential of [1-(11)C]acetate (AC) as a metabolic tracer for renal cell cancer in human subjects.

METHODS

Twenty-one patients with suspected kidney tumours were investigated with AC and dynamic PET. AC uptake was scored on a five-step scale. Tumour localisation was known from CT/MRI. Histology was available in 18/21 patients. The results in these 18 patients are reported.

RESULTS

AC uptake by the tumour was less than (n=11), equal to (n=5) or higher than (n=2) uptake in the surrounding renal parenchyma. Histological tumour types showed a typical distribution, with a predominance of clear cell carcinomas (n=14) and only a small number of papillary cell carcinomas (n=2) and oncocytomas (n=2). Only the benign oncocytomas were highly positive with AC.

CONCLUSION

In most kidney tumours the AC accumulation was not higher than in normal kidney parenchyma. Therefore, AC PET cannot be recommend for the characterisation of a renal mass.

Very stable 188Re-S4 chelates for labelling biomolecules: preparation with highly concentrated perrhenate eluates

AIM

The preparation and stability of a new (188)Re-S(4)-complex [S(4) = (1-aza-18-crown-6)(O)C-C(SH)-C(SH)-C(O)NH-(CH(2))(3)-NH-(CH(2))(3)-NHC(O)-C(SH)-C(SH)-C(O)(1-aza-18-crown-6] was studied at therapeutic relevant radioactive concentrations. The results were compared with (188)Re-MAG(3) (MAG(3): mercaptoacetyltriglycine) and (188)Re-DMSA preparations (DMSA: dimercaptosuccinic acid) performed with the same highly concentrated [(188)Re]perrhenate solution (12-15 GBq/ml).

METHODS

The (188)Re complexes were prepared by direct reduction of perrhenate ((188)Re-S(4)-complex) as well as via the (188)Re-EDTA precursor complex ((188)Re-MAG(3), (188)Re-DMSA). The preparations were stabilised with 15 mg of ascorbic acid and analysed after 1, 2, and 24 hours by TLC and HPLC. Additionally, in vitro and in vivo stability studies were performed with the purified complexes.

RESULTS

After stabilisation with 15 mg of ascorbic acid, all of the complexes were nearly stable under nitrogen for hours, and only 2-8% of perrhenate was observed after 24 h. In contrast, only the (188)Re-S(4) complex was completely stable in vitro and in all investigated in vivo samples after separation of ligand excess and reducing agent by HPLC.

CONCLUSION

The bridging amine group or free carboxylic groups of the S(4)-ligand framework make available reactive positions for coupling biomolecules to the chelate. Thus it appears that the new (188)Re-S(4) complexes offer the possibility of stable and high specific activity labelling of biomolecules for therapeutic application.