Physiological expression of pancreatic somatostatin receptors in 99mTc-HYNIC-TOC scintigraphy.

PURPOSE: To describe the frequency of head and/or pancreas uncinate process uptake of 99mTc-HYNIC-TOC, to study its nature, and analyze its diagnostic value. MATERIALS AND METHODS: Retrospective evaluation of 47 consecutive 99mTc-HYNIC-TOC examinations was conducted. Head and/or pancreas uncinate process uptake was considered to be physiological in patients with normal CT at the same episode and in follow-up. It was analyzed if age or diabetes mellitus was justifying the existence or not of uptake. RESULTS: 32.5% patients showed uptake; 73% of them were mild. 84.6% patients with uptake have no pathology and 4% had neuroendocrine pancreatic disease at CT. Neither the age nor the diabetes mellitus established differences in patients without lesion. CONCLUSIONS: Near one-third of patients show physiological uptake by head and/or pancreas uncinate process at 99mTc-HYNIC-TOC scintigraphy. It seems that neither the diabetes nor the ages are factors that determine this physiological uptake.

Improved radiopharmaceutical based on 99mTc-Bombesin-folate for breast tumour imaging.

BACKGROUND: Clinical studies in women using technetium-99m (Tc)-Bombesin have shown successful radionuclide imaging of breast tumours overexpressing gastrin-releasing peptide receptors (GRPRs). Recent studies have demonstrated that most breast tumours overexpress folate receptors (FRα). AIM: The aim of this work was to synthesize the Lys(α,γ-Folate)-Lys(Tc-EDDA/HYNIC)-Bombesin (1-14) conjugate (Tc-Bombesin-Folate), as well as to assess the in-vitro and in-vivo potential of the radiopharmaceutical to target FRα and GRPR. METHODS: LysLys(HYNIC)-Bombesin (1-14) was conjugated to folic acid and the product was purified by size-exclusion high-performance liquid chromatography. Ultraviolet-visible spectroscopy, Fourier transform infrared spectroscopy and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry were used for chemical characterization. Tc labelling was performed using ethylenediamine-N,N'-diacetic acid/tricine as coligands. In-vitro binding studies were carried out in T47D breast cancer cells (positive for FRα and GRPR). Biodistribution studies and micro-single-photon emission computed tomography/computed tomography imaging were carried out on athymic mice with T47D-induced tumours. RESULTS: High-performance liquid chromatography analyses indicated that the radioconjugate was obtained with high radiochemical purity (96±2.1%). In-vitro and in-vivo results showed significant uptake of the radiopharmaceutical in T47D cells and tumours (5.43% ID/g), which was significantly inhibited by preincubation with cold folic acid or cold Bombesin. CONCLUSION: The Tc-Bombesin-folate heterobivalent radiopharmaceutical significantly enhances in-vivo tumour uptake because of the concomitant interaction with FRα and GRPR.

Synthesis and evaluation of a new 99mTc(I)-tricarbonyl complex bearing the 5-nitroimidazol-1-yl moiety as potential hypoxia imaging agent.

The objective of this work was to develop a novel (99m) Tc complex bearing the 5-nitroimidazol-1-yl moiety with recognised selectivity towards hypoxic tissue, as a potential radiopharmaceutical for imaging tumour hypoxia. The new metronidazole derivative (2-amine-3-[2-(2-methyl-5-nitro-1H-imidazol-1-yl)ethylthio]propanoic acid) (L) containing adequate groups to coordinate technetium through the formation of a Tc(I)-tricarbonyl complex was synthesised with adequate yield (33%) and characterised by spectroscopy. Labelling was performed by substitution of three labile water molecules of the technetium tricarbonyl precursor, fac-[(99m)Tc(CO)3 (H2O)3](+) with the ligand. A radiochemical purity higher than 90% was achieved and remained unchanged for more than 4 h. The complex has a high stability in plasma, a moderate plasma protein binding and a moderate hydrophilicity. In vitro cell uptake studies showed a ratio between the activity taken up by cells in hypoxia/normoxia of 1.6 ± 0.4 (p < 0.5). Biodistribution in normal mice showed rapid depuration and low uptake in all organs and tissues except liver. Biodistribution in mice bearing induced tumours showed a low tumour uptake, but tumour/muscle ratio was favourable thanks to depuration. Comparison with biological results of other metronidazole derivatives clearly shows that modifications of the chelator are very important and contribute to improve the biological behaviour.

Design and biological evaluation of 99mTc-N2S2-Tat(49-57)-c(RGDyK): a hybrid radiopharmaceutical for tumors expressing α(v)ß(3) integrins.

UNLABELLED: The α(ν)ß(3) integrin is over-expressed in the tumor neovasculature and the tumor cells of glioblastomas. The HIV Tat-derived peptide has been used to deliver various cargos into cells. The aim of this research was to synthesize and assess the in vitro and in vivo uptake of (99m)Tc-N2S2-Tat(49-57)-c(RGDyK) ((99m)Tc-Tat-RGD) in α(ν)ß(3) integrin positive cancer cells and compare it to that of a conventional (99m)Tc-RGD peptide ((99m)Tc-EDDA/HYNIC-E-[c(RGDfK)]2). METHODS: The c(RGDyK) peptide was conjugated to a maleimidopropionyl (MP) moiety through Lys, and the MP group was used as the branch position to form a thioether with the Cys(12) side chain of the Tat(49-57)-spacer-N2S2 peptide. (99m)Tc-Tat-RGD was prepared, and stability studies were carried out by size exclusion HPLC analyses in human serum. The in vitro affinity for α(v)ß(3) integrin was determined by a competitive binding assay. In vitro internalization was determined using glioblastoma C6 cells. Biodistribution studies were accomplished in athymic mice with C6 induced tumors that had blocked and unblocked receptors. Images were obtained using a micro-SPECT/CT. RESULTS: (99m)Tc-Tat-RGD was obtained with a radiochemical purity higher than 95%, as determined by radio-HPLC and ITLC-SG analyses. Protein binding was 15.7% for (99m)Tc-Tat-RGD and 5.6% for (99m)Tc-RGD. The IC50 values were 6.7 nM ((99m)Tc-Tat-RGD) and 4.6 nM ((99m)Tc-RGD). Internalization in C6 cells was higher in (99m)Tc-Tat-RGD (37.5%) than in (99m)Tc-RGD (10%). Biodistribution studies and in vivo micro-SPECT/CT images in mice showed higher tumor uptake for (99m)Tc-Tat-RGD (6.98% ± 1.34% ID/g at 3h) than that of (99m)Tc-RGD (3.72%±0.52% ID/g at 3h) with specific recognition for α(v)ß(3) integrins. CONCLUSIONS: Because of the significant cell internalization (Auger and internal conversion electrons) and specific recognition for α(v)ß(3) integrins, the hybrid (99m)Tc-N2S2-Tat(49-57)-c(RGDyK) radiopharmaceutical is potentially useful for the imaging and possible therapy of tumors expressing α(v)ß(3) integrins.

Synthesis, in vitro and in vivo characterization of novel 99mTc-'4+1'-labeled 5-nitroimidazole derivatives as potential agents for imaging hypoxia.

UNLABELLED: The evaluation of oxygenation status of solid tumors is an important field of radiopharmaceutical research. With the aim to develop new potential 99mTc-radiopharmaceuticals for imaging hypoxia, we have synthesized two novel isocyanide derivatives of metronidazole, which has demonstrated high affinity for hypoxic tumors in vitro and in vivo. METHODS: Metronidazole derivatives 4-isocyano-N-[2-(2-methyl-5-nitro-1H-imidazol-1-yl)ethyl]butanamide (M1) and 1-(4-isocyanobutanoyl)-4-[2-(2-methyl-5-nitro-1H-imidazol-1-yl)ethyl]piperazine (M2) were synthesized, and labeling was performed through preparation of their corresponding 99mTc-(4+1) complexes, 99mTc-NS3M1 and 99mTc-NS3M2. The structure of the technetium complexes was corroborated by preparation and characterization of the corresponding rhenium complexes. We have studied the main physicochemical properties (stability, lipophilicity and plasma protein binding). Biological behavior in HCT-15 cells both in oxia and in hypoxia was assessed. Biodistribution in normal mice and in animals bearing induced 3LL Lewis murine lung carcinoma was also studied. RESULTS: Metronidazole derivatives were successfully synthesized. Labeling with high radiochemical purity was achieved for both ligands. 99mTc complexes were stable in labeling milieu and human plasma. However, presence of the piperazine linker in M2 resulted in higher lipophilicity and protein binding. Although cell uptake in hypoxic conditions was observed for both radiotracers, 99mTc-NS3M2 biodistribution was considered unsuitable for a potential radiopharmaceutical due to high liver uptake and poor blood clearance. However, 99mTc-NS3M1 demonstrated a very favorable in vivo profile both in normal mice and in mice bearing induced tumors. CONCLUSION: Selective uptake and retention in tumor together with favorable tumor/muscle ratio make 99mTc-NS3M1 a promising candidate for further evaluation as potential hypoxia imaging agent in tumors.

A portable test system for determination of bacterial endotoxins in 18F-FDG, 99mTc, and lyophilized reagents for labeling with 99mTc.

UNLABELLED: A rapid quantitative kinetic chromogenic test in an automated portable test system has been developed for in-process and end-product determination of bacterial endotoxins in water using the Limulus amebocyte lysate. The aim of this work was to validate the method for (18)F-FDG, (99m)Tc, and the lyophilized reagents methylene diphosphonic acid (MDP) and pyrophosphate for labeling with (99m)Tc radiopharmaceuticals with no interfering factors. METHODS: Experiments were performed on 3 consecutive batches of (18)F-FDG, (99m)Tc, MDP, and pyrophosphate produced at the Nuclear Energy and Research Institute of São Paulo, Brazil, using a portable test system. The maximum valid dilution (=500) was calculated to establish the extent of dilution to avoid interfering test conditions. RESULTS: Better results were obtained above a 1:5 dilution factor for (18)F-FDG and (99m)Tc, 1:20 for MDP, and 1:100 for pyrophosphate. The requirements of the test were satisfied (R ≤ 0.980, recovery of product positive control between 50% and 200%, and coefficient variation of samples < 25%), and the endotoxin concentration was lower than the lowest concentration of the standard curve (0.05 endotoxin unit mL(-1)) and therefore less than the established limit in pharmacopoeias. CONCLUSION: The portable test system is a rapid, simple, and accurate technique using the quantitative kinetic chromogenic method for bacterial endotoxin determination. For this reason, the test is practical for radiopharmaceutical uses and tends to be the method of choice for the pyrogen test. For (18)F-FDG, (99m)Tc, MDP, and pyrophosphate, the validation was successfully performed.

Effects of meal size and proximal-distal segmentation on gastric activity.

AIM: To evaluate the effects of meal size and three segmentations on intragastric distribution of the meal and gastric motility, by scintigraphy. METHODS: Twelve healthy volunteers were randomly assessed, twice, by scintigraphy. The test meal consisted of 60 or 180 mL of yogurt labeled with 64 MBq (99m)Tc-tin colloid. Anterior and posterior dynamic frames were simultaneously acquired for 18 min and all data were analyzed in MatLab. Three proximal-distal segmentations using regions of interest were adopted for both meals. RESULTS: Intragastric distribution of the meal between the proximal and distal compartments was strongly influenced by the way in which the stomach was divided, showing greater proximal retention after the 180 mL. An important finding was that both dominant frequencies (1 and 3 cpm) were simultaneously recorded in the proximal and distal stomach; however, the power ratio of those dominant frequencies varied in agreement with the segmentation adopted and was independent of the meal size. CONCLUSION: It was possible to simultaneously evaluate the static intragastric distribution and phasic contractility from the same recording using our scintigraphic approach.

ABC transporters during epilepsy and mechanisms underlying multidrug resistance in refractory epilepsy.

It is estimated 20-25% of the epileptic patients fails to achieve good control with the different antiepileptic drugs (AEDs) treatments, developing refractory epilepsy (RE). Discovered first in cancer, the activity of P-glycoprotein (P-gp) and others ABC transporters as multidrug-resistance-associated proteins (MRPs) and breast cancer resistant protein (BCRP) are directly related with the refractoriness. We have observed the overexpression of these all transporters in the brain of patients with RE, and according with other authors, all these data suggests an active drug efflux from brain. Both constitutive and seizure induced brain P-gp overexpression was also suggested. As confirmation of these clinical evidences, different models of experimental epilepsy have demonstrated P-gp overexpression on blood brain barrier (BBB) and brain parenchyma cells, as astrocytes and neurons. In our model, early P-pg detection in vessel-related cells and later additional P-gp detection in neurons, correlated with the gradual loss of protective effect of phenytoin. The progressive neuronal P-gp expression, depending on intensity and time-constancy of seizure-injury, was in agreement with the development of "P-gp-positive seizure-axis" proposed by Kwan & Brodie, who also showed that the development of RE directly correlated with the number and frequency of seizures before initiation of drug therapy. P-gp expression in excretory organs suggests that P-gp have a central role in drug elimination. Persistent low levels of AEDs in plasma and P-gp brain overexpression in several RE pediatric patients were reported. We also observed in adult RE patients, an increased liver clearance of 99mTc-hexakis-2-methoxyisobutylisonitrile (99mTc-MIBI) (a P-gp substrate), and the surgically treated cases showed P-gp brain overexpression. These results suggest the systemic hyperactivity of P-gp in RE patients, including brain P-gp over-expression should be suspected when persistent subtherapeutic levels of AEDs in plasma are detected. P-gp neuronal expression described in both clinical and experimental reports indicates that additional mechanisms could be operative from seizure-affected P-gp-positive neurons, due to AEDs targets are expressed at membrane level. An alternative mechanism was demonstrated in P-gp-expressed cells that exhibit lower membrane potential (Deltapsi(0)=-10 to -20) compared to normal physiological Deltapsi(0) of -60 mV. Under this situation and irrespective to the P-gp pharmacoresistant property or type of drug treatment selected, P-gp-expressed neurons could increase their sensitivity to new seizures perhaps as an epileptogenic mechanism. The understanding of properties of these ABC transporters can offer new tools for better selection of more effective preventive or therapeutic strategies and avoid the invasive surgical treatments for RE.

Effect of an extract of cauliflower (leaf) on the labeling of blood elements with technetium-99m and on the survival of Escherichia coli AB1157 submitted to the treatment with stannous chloride.

The labeling of red blood cells (RBC) with technetium-99m (99mTc) depends on a reducing agent and stannous chloride (SnCl(2)) and is widely utilized. This labeling may also be altered by drugs, and SnCl(2) reduces the survival of Escherichia coli cultures. Cauliflower (Brassica oleracea L. var. botrytis) is used in folk medicine and we evaluated its influence on (i) the labeling of blood elements with 99mTc, and (ii) on the survival of an E. coli strain. Blood was withdrawn from rats that drank the extract of cauliflower (15 days). Blood was incubated with SnCl(2) and with 99mTc, as sodium pertechnetate, centrifuged and plasma (P) and RBC were isolated. Samples of P and RBC were also precipitated, centrifuged and soluble and insoluble fractions isolated. E. coli culture was treated with SnCl(2) in the presence of cauliflower. The extract of cauliflower did not alter the fixation of 99mTc on blood fractions; however, it abolished the lethal effect of SnCl(2) on the E. coli culture. We suggest that the substances present in the extract of cauliflower probably, would have redox property with different mechanisms of action. The oxidant action of the substances of the extract would not be strong enough to oxidise the stannous ions altering the 99mTc-labeling. However, the referred substances could oxidise these ions sufficiently to protect the E. coli culture against the lethal effect of the stannous ion.

Excreçäo de 99mTc DISIDA pelo trato biliar no diagnóstico etiológico da colestase neonatal / Excrection of 99m Tc DISIDA in the hepatobiliary scintigraphy in etiological diagnosis of neonatal cholestasis

Foram avaliados 51 testes de excreçäo de 99mTc-DISIDA pelo trato biliar em pacientes com colestase neonatal. O objetivo deste trabalho foi determinar o valor do teste no diagnóstico diferencial desta síndrome, correlacionado-os com os dados clínicos e laboratoriais encontrados. Os casos estudados foram divididos em dois grupos: atresia de vias biliares extra-hepáticas, 26 pacientes (50,9 por cento) e näo-atresia de vias biliares extra-hepáticas, 25 pacientes (49,1 por cento). Analisando os resultados, observou-se que o referido teste teve sensibilidade de 96 por cento, especificidade de 56 por cento, valor preditivo positivo de 69 por cento, valor preditivo negativo de 93 por cento e acurácia de 76,5 por cento. A acurácia do teste mostrou-se inferior somente à biopsia hepática. Em conclusäo a cintilografia mostrou-se bastante útil na definiçäo de atresia de vias biliares extra-hepáticas, com menor valor no grupo das hepatites neonatais, talves pelo encaminhamento tardio dos pacientes, tempo curto de estudo cintilográfico ou fatores relacionados à própria etiologia do processo

Update on dimercaptosuccinic acid renal scanning in children with urinary tract infection.

The dimercaptosuccinic acid (DMSA) renal scan is a method for assessing kidney function. Indications for DMSA scanning in children with urinary tract infection (UTI), as well as timing, have changed. Pitfalls in interpreting DMSA scans include: (1) acute pyelonephritis (APN), (2) tubular dysfunction, (3) hypertension, (4) use of captopril in patients with renovascular hypertension and (5) duplex kidneys. Interpretation of DMSA scans in children with UTI vary according to timing and clinical setting. During the course of a febrile UTI a DMSA scan may reveal a normal kidney, APN or a non-functioning, small and/or ectopic kidney. In the absence of UTI (up to 6 months) in children with vesicoureteric reflux a DMSA scan may indicate a normal kidney, renal scarring (reflux nephropathy), occult duplex kidney and allows the progression of scarring and hypertrophy of normal areas of the kidney to be followed anatomically. The DMSA renal scan in now the most reliable test for the diagnosis of APN. The transient abnormalities due to APN can occur in normal or scarred kidneys. Lesions due to reflux nephropathy (defined as a defect in the renal outline or contraction of the whole kidney) are permanent. Intravenous urography reveals renal abnormalities later than the DMSA scan. If abnormalities are seen on a DMSA scan performed during the course of APN it is impossible to predict the outcome: they can progress to permanent scarring or heal completely. An abnormal DMSA scan during a febrile UTI allows the identification of children at risk of developing renal scars. These children should be carefully investigated, maintained on long-term quimioprophylaxis and followed.

[Excretion of 99m Tc-DISIDA through the bile ducts in the etiological diagnosis of neonatal cholestasis]. / Excreção de 99mTc-DISIDA pelo trato biliar no diagnóstico etiológico da colestase neonátal.

We evaluated 51 tests of 99mTc-DISIDA excretion by the biliary tree in patients with neonatal cholestasis. The aim of the present study was to verify the value of this test in the differentiation of this syndrome, correlating it to the clinical and laboratory data. The case studied were divided into two groups: extrahepatic biliary atresia, 26 patients (50.9%) and no-extrahepatic biliary atresia, 25 patients (49.1%). Analyzing the results, we concluded that this test had 96% sensitivity, 56% specificity, 69% positive predictive value, 93% negative predictive value and 76.5% accuracy. The accuracy of this test was only lower than that of hepatic biopsy. We conclude that the hepatobiliary scintigraphy was very useful in the definition of extrahepatic biliary atresia, with less value in the group of neonatal hepatitis, perhaps due to the delayed referral of the patients, short time of the scintigraphy study or factors related to the etiology of cholestasis itself.