Single isomer technetium-99m tamoxifen conjugates.

To produce an imaging agent for breast cancer using a technetium-99m-labeled agent specific for estrogen receptors, an N(2)S(2) bifunctional chelator was conjugated to Z- and E-aminotamoxifens through an amide linker. These bioconjugates have been chelated with both technetium-99m and rhenium. For the Z-isomer, chelation with rhenium in the presence of sodium acetate yields a mixture of two isomers, anti and syn, in a 1:1 ratio and in the presence of hydroxide results in only the anti isomer. Both the Z- and E-tamoxifen conjugates have been chelated with technetium-99m at the tracer level yielding a single isomer product, which is assigned as anti based on chromatographic comparison to the rhenium complexes. Radiochemical yields were consistently greater than 80%, with Sep-Pak column purification yielding a final product with >99% radiochemical purity and no residual starting material. Both in vitro and in vivo biological evaluation of the tamoxifen chelates indicated very limited estrogen receptor binding.

An N2S2 bifunctional chelator for technetium-99m and rhenium: complexation, conjugation, and epimerization to a single isomer.

A bifunctional chelator 6 was prepared bearing an N2S2 core for binding rhenium or technetium and a carboxylic acid group for conjugation to amino groups of biomolecules. Complexation of 6 with rhenium(V) resulted in two kinetic isomers, anti-7 and syn-7, being formed in approximately equal amounts. Epimerization with 0.5 M NaOH yields a single isomer anti-7, as determined by NMR spectroscopy and single-crystal X-ray analysis. The 99mTc complex was prepared at the tracer level by reaction of the ligand with 99mTcO4-, tin(II) chloride and sodium gluconate giving a mixture of two isomers, but showing a preference for the anti isomer. Chelation in the presence of 1 M NaOH results in anti-8 being formed as the sole product. The bifunctional ability of the ligand was explored by amide formation with (S)-alpha-phenethylamine, either by direct DCC coupling or through the N-hydroxy succinimidyl ester 9 intermediate. The deprotected bioconjugate 11 was complexed with rhenium, yielding similar amounts of two isomeric rhenium complexes, anti-12 and syn-12, which were isolated and characterized by NMR spectroscopy. Treatment of the kinetic mixture of anti-12 and syn-12 with 1 M NaOH resulted in quantitative conversion to a single rhenium complex anti-12. With technetium-99m in 0.1 M sodium acetate, bioconjugate 11 yielded both technetium-99m complexes anti-13 and syn-13, in a 2:1 ratio, respectively. In contrast, complexation in the presence of 1 M NaOH gave only one technetium-99m complex, assigned the structure anti-13.

Radioiodinated 2-nitrobenzyl carbamates as bioreductive alkylating agents for tissue hypoxia.

Three N-methylcarbamates of iodonitrobenzyl alcohols (4-iodo-2-nitrobenzyl alcohol 2, 5-iodo-2-nitrobenzyl alcohol 3 and 4-iodo-2,6-dinitrobenzyl alcohol 4) bearing [125I] have been prepared and characterized for their lipophilicity, their reduction potentials and the in vivo liability of the radioiodine in healthy mice. Based upon these results, 2 and 4 were tested in tumour-bearing mice showing limited uptake of radioactivity in tumours and a tumour-to-blood ratio of less than 1. Consequently these particular carbamates are not satisfactory as hypoxia imaging agents.

A potential imaging agent for the GABAA receptor: 4-t-butyl-1-(4-[123I]iodophenyl)-2,6,7-trioxabicyclo-[2.2.2]octane.

Based upon the known high toxicity and high antagonist activity of t-butylorthobenzoates towards the GABA receptor complex, 4-t-butyl-1-(4-iodophenyl)-2,6,7-trioxabicyclo[2.2.2]octane 5 and its radioiodo analogues ([123I]-5 and [131I]-5 were prepared as potential markers for the gated chloride channel of GABAA receptors. Mice showed rapid clearance of [131I]-5 from all organs including the brain. The radioactivity was found to proceed into the urine in spite of the high lipophilicity of 5, the high binding affinity of 5 for plasma protein and the apparent chemical stability of 5 in plasma.

[Intravascular echography in interventional vascular radiology]. / L'ecografia intravascolare nella radiologia interventistica arteriosa.

Intravascular US studies were performed with a 20 MHz rotating transducer mounted on a long flexible shaft in 14 patients undergoing interventional vascular procedures--i.e. percutaneous transluminal angioplasty (PTA), atherectomy with a Simpson device, and Palmaz stent placement. Intravascular US was used immediately before the procedure to assess the lesion characteristics and during and after the procedure to verify its results. In PTA, intravascular US clearly shows the fracture of the plaque, its separation from the medial layer, and the total longitudinal extension of the intimal flaps. Palmaz stents are clearly shown and their correct positioning on the arterial wall is therefore precisely evaluated. After atherectomy, intravascular US shows the changes in wall thickness and identifies the areas where more tissue needs to be removed. Intravascular US appears to be a very promising technique for monitoring and directing revascularization procedures by helping select the correct interventional procedure. The initial limitation of use of intravascular ultrasound catheters to straight arterial segments has been resolved by the development of over-the-wire catheters. Further technical development and clinical research are needed.

Amino and iodotamoxifens: synthesis, estrogen receptor affinity and biodistribution.

Both geometrical isomers (E and Z) of an aminotamoxifen (2) have been prepared as precursors of the corresponding E and Z iodotamoxifens (1). The ability of E and Z-1 and 2 to compete with [3H]estradiol for estrogen receptors in rat uterine cytosol was measured relative to Z-tamoxifen and estradiol. The four tamoxifen derivatives showed affinities ranging from 50% to 1600% of that of tamoxifen. Under the same conditions, tamoxifen's relative binding affinity was 0.2% of that of estradiol. Preparative routes to the radioiodo-tamoxifens, [131I]-E and Z-1, were also developed and provided approximately 100 MBq of 'no carrier added' material in 40-60% radiochemical yield. Study of the biodistribution of these radioligands in tumor-bearing mice demonstrated significant radioactivity in the tumors and in the uterus. For [131I]-E-1, target to background ratios reached 28 for uterus/blood and 10 for tumor/blood; corresponding optimum ratios for [131I]-Z-1 were 10 and 5. A washout study using estradiol indicated selective uptake in the uterus of Swiss white mice. However, tumor uptake and image contrast in humans following intravenous administration of either [131I]-E or Z-1 were insufficient to allow diagnostic use of the radioiodotamoxifens.

Preparation and evaluation of radioiodinated (iodophenyl)cholines and their morpholinium and piperidinium analogues as myocardial perfusion imaging agents.

A series of nine radioiodinated quaternary ammonium salts related to phenylcholine were synthesized, characterized, and radiolabeled by exchange. These compounds were evaluated as myocardial perfusion imaging agents in mice, pigs, and humans. Mice biodistribution studies showed that five of the nine compounds were taken up in the heart to the same extent as 201Tl+ at 5 min. At 60 min myocardial retention was significantly better than 201Tl+ for six of the compounds. Several of the compounds showed more favorable heart/blood and heart/liver ratios when compared to 201Tl+. Evaluation of three of the more promising compounds in pigs and humans however revealed no selective myocardial uptake.

Percutaneous removal of caliceal and other "inaccessible" stones: results.

Percutaneous removal of renal stones (percutaneous nephrolithotomy) is becoming an established procedure, especially for stones lying free in the renal pelvis. However, some renal stones, particularly caliceal stones, are less accessible and, therefore, more difficult by the percutaneous route. We removed percutaneously 95 caliceal or otherwise poorly accessible renal stones from 53 patients with a variety of techniques, including percutaneous puncture above the 12th rib, double or Y percutaneous nephrostomy tracts, rigid and flexible endoscopy, and intrarenal cutting with diathermy. Intravenously assisted local anesthesia was used exclusively in 89 per cent of the patients. Status free of stones was achieved in all but 1 patient who retained 2 small fragments. The average number of sessions was 1.89 and the average hospital stay was 7.9 days. Complications were minor except for 1 patient who required tertiary renal artery embolization for bleeding. Illustrative cases are presented. Virtually all renal stones can be removed percutaneously.

Percutaneous nephrolithotomy: extraction of renal and ureteral calculi from 100 patients.

A percutaneous nephrostomy tract was used as a conduit to the kidney and ureter for extraction of 149 calculi in 100 patients. A variety of grasping and fragmentation techniques under fluoroscopic and endoscopic control were used to extract calculi in 88 per cent of the patients. With experience, operator efficiency and rate of stone extraction increased from 76 per cent early in the series to 91 per cent in the most recent patients, and the incidence of complications decreased from 17 to 5 per cent. Percutaneous removal of upper tract urinary calculi appears to be an appropriate alternative to an open operation in most patients with symptomatic urolithiasis.

Murine model for study of cell-mediated immunity: protection against death from fully virulent Francisella tularensis infection.

To assess cell-mediated immunity in terms of host protection, an experimental model was developed in which passively transferred spleen cells from immunized AKR/J mice enabled nonimmume syngeneic recipients to survive an otherwise fatal infection with fully virulent Francisella tularensis. Donor immunization was achieved by administering live attenuted tularemia vaccine and, subsequently, the virulent streptomycin-sensitive SCHU S4 strain of F. tularensis. At selected intervals after immunization, donor spleen cells were transferred to streptomycin-treated recipients challenged subcutaneously, intravenously, or intraperitoneally with 25 to 50 minimal lethal doses of virulent streptomycin-resistant F. tularensis SCHU S5. The protection afforded by immune spleen cells was maximal (essentially 100%) 12 days after the SCHU S4 secondary immunization.