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T J McCarthy,
W A Banks,
C L Farrell,
S Adamu,
C P Derdeyn,
A Z Snyder,
R Laforest,
D C Litzinger,
D Martin,
C P LeBel,
M J Welch
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ABSTRACT: Human obesity may be caused by a resistance to circulating leptin. Evidence from rodents and humans suggests that a major component of this resistance is an impairment in the ability of the blood-brain barrier (BBB) to transport leptin from the blood to the brain. One potential way to bypass the BBB is by administering leptin into the intrathecal (i.t.) space. To be effective, i.t. leptin would have to move caudally from the site of injection, enter the cranium, and reach the hypothalamic arcuate nucleus at the base of the pituitary fossa. However, many substances, especially small, lipid-soluble molecules, do not diffuse far from the site of i.t. injection but are resorbed back into blood. To determine whether i.t. leptin can move caudally, we injected leptin conjugated to diethylenetriaminepentaacetic acid (DTPA) and labeled with (68)Ga (G-Ob) into the lumbar space of three baboons. We also studied unconjugated DTPA labeled with (68)Ga, which did not move up the spinal cord but rapidly appeared in blood after i.t. injection. In contrast, G-Ob steadily moved toward the cranium and had reached the hypothalamus 91 and 139 min after i.t. injection in two baboons. We estimated the concentration of leptin in the hypothalamic region to be at least 8 ng/ml, which is about 40 times higher than cerebrospinal fluid levels in normal weight humans and about 4 times higher than the highest level ever recorded after the peripheral administration of leptin. In a third baboon, the leptin neither moved caudally nor appeared in the blood. We conclude that leptin administered i.t. can reach the hypothalamus in therapeutic concentrations, although there is considerable individual variation.
Journal of Pharmacology and Experimental Therapeutics 07/2002; 301(3):878-83. · 3.83 Impact Factor
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ABSTRACT: Recent studies suggest that viral interleukin 10 suppresses alloimmune response in transplantation and that cationic lipids are one of the most promising nonviral vehicles for gene therapy. The aim of this study was to examine the effect of ex vivo lipid-mediated viral IL10 gene transfer into rat lung allografts on subsequent rejection.
Male F344 rats (RT1lvl) underwent left lung transplantation with allografts from Brown Norway rats (RT1n). Allografts were transvascularly transfected 15 minutes after harvest with 5 mL of 1:20-diluted (group 1, n = 7) or 1:40-diluted (group 2, n = 6) GL67-pCMVievIL-10 complex. Group 3 (n = 7), serving as the control group, received 1:40-diluted GL67-pCF1-chloramphenicol acetyltransferase complex. All allografts were preserved for 3 hours at 10 degrees C before transplantation. In all groups recipients were killed on postoperative day 5. Transgene expression of viral interleukin 10 was assessed by means of both reverse transcriptase-polymerase chain reaction and immunohistochemistry. Histologic rejection score, allograft gas exchange, exhaled nitric oxide level, and allograft cytokine mRNA expression were also assessed.
Dose-dependent transgene expression of viral interleukin 10 was detected by means of both reverse transcriptase-polymerase chain reaction and immunohistochemistry. Allograft gas exchange (PaO2) in groups 1 (114.06 +/- 61.1 mm Hg) and 2 (108.58 +/- 35.7 mm Hg) was significantly better than that in group 3 (66.4 +/- 8.22 mm Hg; P =.020 and P =.023, respectively). The vascular rejection score in group 1 was significantly lower than that in group 3 (P =.032, Kruskal-Wallis test). Exhaled nitric oxide levels in group 2 (5.150 +/- 6.38 ppb) were significantly lower than those in group 3 (13.517 +/- 10.4 ppb; P =.039). Allograft interleukin 2 mRNA expression levels in group 1 (1.123 +/- 0.23 relative units) were significantly lower than those in group 3 (1.753 +/- 0.71 relative units; P =.038 vs group 3).
Lipid-mediated ex vivo viral IL10 gene transfer into rat lung allografts improved graft gas exchange, reduced histologic rejection scores, downregulated graft interleukin 2 mRNA expression, and reduced exhaled nitric oxide levels by postoperative day 5. These results suggest a therapeutic potential of graft viral IL10 gene transfer as an effective immunosuppressive strategy against lung allograft rejection.
Journal of Thoracic and Cardiovascular Surgery 08/2001; 122(1):29-38. · 3.41 Impact Factor
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ABSTRACT: Recent studies suggest that viral interleukin-10 (vIL-10) suppresses alloimmune response in transplantation. Tissue mRNA expression of inducible nitric oxide synthase (iNOS) and exhaled nitric oxide (NO) levels have been observed to increase in lung allograft rejection. The aims of this study were to examine the feasibility of vIL-10 gene transfer into rat lung allografts and to investigate its effect on subsequent allograft rejection.
Male Lewis rats (RT1l) underwent left lung transplantation with allografts from Brown Norway rats (RT1n). The donor rats were endobronchially transfected 2 minutes before harvest with 400 microg (group I, n = 5), 600 microg (group II, n = 5), or 800 microg (group III, n = 5) of naked pCMVievIL-10. Group IV (n = 5) animals, serving as control, received 400 microg of naked pCF1-CAT. All recipients were sacrificed on postoperative day 5. Transgene expression of vIL-10 was assessed by both reverse transcriptase-polymerase chain reaction and immunohistochemistry. Allograft gas exchange, exhaled NO level, histologic rejection score, and mRNA expression of graft cyokines were also assessed.
Transgene expression of lung graft vIL-10 was detected by both reverse transcriptase-polymerase chain reaction and immunohistochemistry. The iNOS mRNA expression in groups I, II, and III was significantly lower than that of group IV (p < 0.05, analysis of variance). Exhaled NO levels in groups I, II, and III were significantly lower than in group IV (p < 0.01, analysis of variance). There was no significant difference between groups with respect to gas exchange, peak airway pressure, or histologic rejection score.
It appears that endobronchial transfection of naked vIL-10 plasmid in a rat lung allotransplant model is feasible and suppresses lung iNOS mRNA expression and exhaled NO levels. An association between iNOS upregulation and high exhaled NO levels in lung allograft resection was also noted.
The Annals of Thoracic Surgery 04/2001; 71(4):1126-33. · 3.74 Impact Factor
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ABSTRACT: The objective of this study was to examine the feasibility of human interleukin 10 gene transfer into rat lung isografts and to investigate the effect of gene transfer on subsequent ischemia-reperfusion injury.
Male F344 rats were divided into 4 groups and underwent left lung isotransplantation. Twenty-four hours before harvest, 5 x 10E9 pfu (group I, n = 6) or 1 x 10E10 pfu (group II, n = 7) of AdRSVhIL-10 was intravenously administered to donor rats. In group I-C (n = 6) and group II-C (n = 6), serving as controls, 5 x 10E9 pfu and 1 x 10E10 pfu of AdCMVLacZ were administered, respectively. Grafts were preserved for 18 hours at 4 degrees C before implantation and assessed 24 hours after reperfusion. Transgene expression of human interleukin 10 was assessed by both reverse transcriptase-polymerase chain reaction and immunohistochemistry. Graft inducible nitric oxide synthase, tumor necrosis factor alpha, intercellular adhesion molecule-1, growth-regulated gene product/cytokine-induced neutrophil chemoattractant-1, and monocyte chemotactic protein-1 mRNA expression were assessed by reverse transcriptase-polymerase chain reaction. Isograft gas exchange, exhaled nitric oxide, and myeloperoxidase activity were also analyzed.
Dose-dependent transgene expression was detected by reverse transcriptase-polymerase chain reaction and immunohistochemistry. Arterial PO (2) in groups I (164.72 +/- 85.3 mm Hg) and II (153.19 +/- 113 mm Hg) was significantly higher than in groups I-C (82.37 +/- 19.1 mm Hg) and II-C (77.95 +/- 33.4 mm Hg) (P =.022 and P =.031, respectively). Arterial PCO (2) in group I (33.40 +/- 6.80 mm Hg) was significantly lower than in group I-C (51.23 +/- 11.9 mm Hg) (P =.0096). Myeloperoxidase activity in group II (0.083 +/- 0.031 DeltaOD. min(-1). mg(-1)) was significantly lower than in group II-C (0.117 +/- 0.028 DeltaOD. min(-1). mg(-1)) (P =.044). The inducible nitric oxide synthase mRNA expression in group II (0.627 +/- 0.28) was significantly lower than in group II-C (1.125 +/- 0.63) (P =. 039).
Adenovirus-mediated human interleukin 10 gene transfer in vivo into lung isografts ameliorates subsequent ischemia-reperfusion injury. This results in improved graft gas exchange, reduced neutrophil sequestration, and down-regulation of graft inducible nitric oxide synthase mRNA expression.
Journal of Thoracic and Cardiovascular Surgery 12/2000; 120(5):947-56. · 3.41 Impact Factor
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ABSTRACT: Angiotensin-converting enzyme (ACE) inhibition attenuates pulmonary hypertension and delays the development of pulmonary vascular remodeling in animal models. Thus, ACE inhibition might be a useful treatment for primary pulmonary hypertension (PPH). To determine the dose of ACE inhibitor required to specifically block pulmonary ACE in humans, we measured the combined forward rate constant (CFRC) for [(18)F]-fluorocaptopril, which is proportional to the mass of ACE in the lung, using positron emission tomography (PET). In five normal subjects, CFRC was measured twice, 1 wk apart, to assess measurement reproducibility. The CFRC was 0.151 +/- 0.067 for the first measurement and 0.140 +/- 0.060 for the second measurement (p = not significant [NS]). In five normals, CFRC decreased on average 84%, from 0.177 +/- 0.053/s to 0.028 +/- 0.017/s (p < 0.05), after 1 wk ingestion of 5 mg enalapril orally once a day (the scans were performed 24 h after the last medication). Similarly, in five patients with PPH, CFRC decreased on average 76%, from 0.052 +/- 0. 020/s to 0.012 +/- 0.003 (p < 0.01), after 1 wk enalapril, despite much lower baseline values. We conclude that the total mass of pulmonary ACE appears to be significantly reduced in PPH and that only low doses of ACE inhibitors may be needed to block the effects of ACE on vascular remodeling in PPH.
American Journal of Respiratory and Critical Care Medicine 06/2000; 161(6):2019-25. · 11.08 Impact Factor
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Journal of Nuclear Medicine 03/2000; 41(2):315-7. · 6.38 Impact Factor
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ABSTRACT: Increased nitric oxide production accompanies acute lung allograft rejection. Transforming growth factor-beta1 is an immunosuppressive cytokine capable of ameliorating acute rejection. The purpose of this study was to determine whether exhaled nitric oxide (eNO) concentrations correlated with the degree of acute rejection.
A model of acute lung transplant rejection in the rat was developed, and concentrations of eNO were measured at the time of animal sacrifice. In group 1 (partial immunosuppression), donor lungs were pretreated with transforming growth factor-beta1 before implantation. In group 2 (fulminant acute rejection), no immunosuppression was used. In group 3 (full immunosuppression), recipients received cyclosporine. Group 4 were normal rats.
When measured from both lungs, eNO concentrations were 4.97+/-0.68 versus 6.73+/-2.90 ppb for groups 1 and 2, respectively (p = 0.58). When measured selectively from transplanted left lungs, eNO concentrations were 8.61+/-0.97 versus 42.14+/-7.27 ppb, respectively (p<0.001). In groups 3 and 4, eNO concentrations were 1.02+/-0.21 and 1.51+/-0.74 ppb, respectively.
Exhaled nitric oxide is elevated in fulminant acute rejection, is reduced after partial immunosuppression using transforming growth factor-beta1 gene therapy, and is in the normal range in cyclosporine-treated animals. The measurement of eNO correlates with the degree of acute lung allograft rejection and may serve as a noninvasive measure of acute lung transplant rejection in the clinical setting.
The Annals of Thoracic Surgery 02/2000; 69(1):210-5. · 3.74 Impact Factor
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ABSTRACT: Responses to inhaled nitric oxide (iNO) in acute lung injury (ALI), as evidenced by improvements in oxygenation, are variable. We hypothesized that the effect of iNO may be related to the pre-iNO distribution of pulmonary blood flow (PBF). In the present study we evaluated the effect of iNO on PBF in normal healthy dogs and in a canine model of ALI induced by oleic acid (OA). In Group "OA only" (n = 5), ALI was induced by central venous injection of 0.08 ml/kg OA. In Group "E+OA" (n = 5), hypoxic pulmonary vasoconstriction after ALI was blocked with low-dose endotoxin (15 microg/kg of Escherichia coli endotoxin) administered 30 min before giving the same dose of OA. Measurements of regional PBF and lung water concentration (LWC) using positron emission tomography (PET) and H215O were performed before and after OA or placebo, and then again at concentrations of 10, 40, and 0 ppm iNO. One hundred twenty minutes after OA injury, PaO2/FIO2 fell significantly in Group OA only, from 567 +/- 32 to 437 +/- 67 mm Hg. In these animals, PBF redistributed from the dorsal edematous regions of the lungs to the nondependent zones, thus partially preserving normal ventilation/ perfusion relationships. As in the normal animals, in Group OA only, iNO did not significantly change either PBF or oxygenation. In Group E+OA, the administration of low-dose endotoxin eliminated perfusion redistribution from the dorsal edematous lung regions. As a result, PaO2/FIO2 fell from 558 +/- 70 to 119 +/- 53 mm Hg, a decrease that was significantly greater than that in Group OA only. In Group E+OA, administration of iNO restored perfusion redistribution to a similar level as in Group OA only, which was associated with a significant improvement in PaO2/FIO2, from 119 +/- 53 to 251 +/- 159 (10 ppm iNO), and 259 +/- 165 mm Hg (40 ppm iNO). We conclude that the effect of iNO on oxygenation after ALI depends on the pre-iNO perfusion pattern, which may help explain the variable response to iNO often observed in patients with acute respiratory distress syndrome.
American Journal of Respiratory and Critical Care Medicine 03/1999; 159(2):563-70. · 11.08 Impact Factor
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ABSTRACT: We have evaluated Cu-diacetyl-bis(N4-methylthiosemicarbazone) (Cu-ATSM), an effective marker for the delineation of hypoxic but viable tissue, in vitro in the EMT6 carcinoma cell line under varying degrees of hypoxia and compared it with the flow tracer 64Cu-pyruvaldehyde-bis(N4-methylthiosemicarbazone) (Cu-PTSM) and the hypoxic tracer 18F-fluoromisonidazole (MISO). We have also compared the uptake of Cu-ATSM and Cu-PTSM in vivo and ex vivo in a murine animal model bearing the EMT6 tumor.
Uptake of 64Cu-ATSM, 64Cu-PTSM and 18F-MISO in vitro into EMT6 cells was investigated at the dissolved oxygen concentrations of 0, 1 x 10(3), 5 x 10(3), 5 x 10(4) and 2 x 10(5) ppm. Biodistribution performed at 1, 5, 10, 20 and 40 min compared 64Cu-ATSM with 64Cu-PTSM in BALB/c mice bearing EMT6 tumors. To determine long-term retention of 64Cu-ATSM, biodistribution was also performed at 1, 2 and 4 h. Ex vivo autoradiography of tumor slices after co-injection of 60Cu-PTSM (60Cu, T1/2 = 23.7 min) and 64Cu-ATSM (64Cu, t1/2 = 12.7 h) into the same animal was performed.
After 1 h, 64Cu-ATSM was taken up by EMT6 cells: 90% at 0 ppm, 77% at 1 x 10(3) ppm, 38% at 5 x 10(3) ppm, 35% at 5 x 10(4) ppm and 31% at 2 x 10(5) ppm. 18F-MISO also showed oxygen concentration dependent uptake, but with lower percentages than 64Cu-ATSM. 64Cu-PTSM showed 83%-85% uptake into the cells after 1 h, independent of oxygen concentration. Biodistribution data of 64Cu-ATSM and 64Cu-PTSM showed optimal tumor uptake after 5 and 10 min, respectively (0.76% injected dose (ID)/organ for 64Cu-ATSM and 1.11%ID/organ for 64Cu-PTSM). Ex vivo imaging experiments showed 60Cu-PTSM uniform throughout the EMT6 tumor, but heterogeneous uptake of 64Cu-ATSM, indicative of selective trapping of 64Cu-ATSM into the hypoxic tumor cells.
Cu-ATSM exhibits selectivity for hypoxic tumor tissue both in vivo and in vitro and may provide a successful diagnostic modality for the detection of tumor ischemia.
Journal of Nuclear Medicine 02/1999; 40(1):177-83. · 6.38 Impact Factor
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ABSTRACT: Thirty years ago Michel M. Ter-Pogossian and Henry N. Wagner, Jr. wrote an article that was published in Nucleonics on the cyclotron production of isotopes for biomedical research. In this report we use the Nucleonics paper as the framework to relate their predictions to the current state of the art, we have broken this into four key areas; commercially available cyclotrons, costs of operating cyclotron facilities, the emergence of compact accelerators, and the cyclotron production of long-lived radionuclides for therapeutic applications. Companies producing cyclotrons commercially are; General Electric Medical Systems, CTI Cyclotron Systems, EBCO, IBA, NNK/Oxford Instruments, and Japan Steel Works. The majority of these machines are now negative ion systems, which allows the option of dual irradiation of two targets. All have a modular design, which allows the system to be customed to a particular facility's need. Cyclotron facility costs have increased dramatically since 1966. We have determined that the bulk of the increase lies in the costs to establish and staff the facility. Increased regulation by Federal and State organizations has severely impacted operational expenses. The growing demand for PET radiopharmaceuticals in the clinical arena has increased the staffing requirements of the facility. Surprisingly, the costs of cyclotrons have not increased (in terms of real dollars) especially when one considers the much greater sophistication in target design, automation, and computer control that has occurred during this time. Innovative approaches are being taken to develop low energy accelerators that are capable of producing PET isotopes. These are easier to operate and less expensive than commercially available cyclotrons. Although many of these systems have been developed, none have as yet gained commercial recognition. A number of groups have begun to address the production of longer lived isotopes on biomedical cyclotrons. Development of this technology may well help to further progress in targeted radiotherapy. We present an overview of potentially useful isotopes.
Seminars in Nuclear Medicine 08/1998; 28(3):235-46. · 4.31 Impact Factor
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ABSTRACT: Radiolabeling of the somatostatin analog octreotide was attempted with p-[18F]fluorophenacyl bromide ([18F]FPB). Following these unsuccessful trials, the reactivity of FPB was studied using benzyl mercaptan, phenyl acetic acid, benzyl alcohol, and benzyl amine as model compounds for amino acid functional groups. Structure and purity of products, relative reactivity of FPB in competition reactions, and radiolabeling experiments are described. In addition, improvement in labeling efficiency of HSA using [18F]FPB was achieved by pretreatment with 2-iminothiolane.
Applied Radiation and Isotopes 08/1997; 48(7):907-16. · 1.17 Impact Factor
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ABSTRACT: Reports have implicated neuronal nitric oxide synthetase (nNOS) in the pathological effects of neurodegenerative diseases. S-Methyl-L-thiocitrulline (MTICU), a potent and selective nNOS inhibitor (Ki = 1.2 nM), was chosen as our initial target molecule for positron emitter labeling as a potential nNOS tracer. We report the synthesis, biological evaluation and primate brain images of S-[11C]methyl-L-thiocitrulline ([I11C]MTICU).
The two-step synthesis of [11C]MTICU consisted of the S-alkylation of alpha-N-Boc-L-thiocitrulline t-butyl ester with [11C]Mel followed by TFA hydrolysis and HPLC purification. The final product was obtained within 50 min (yield = 9.1%-12.5%, based on [11C]Mel S.A. = 27-680 Ci/mmol at end of synthesis). The lipophilicity of [11C]MTICU was determined by octanol/water partition coefficient (LogP). Blood stability of this tracer in vitro and in vivo was measured by HPLC analysis. Biodistribution using female Sprague-Dawley rats was performed, including examination of uptake in cerebellum and olfactory bulb (high nNOS) as well as cortex and brain stem (low nNOS). Carbon-11-MTICU was administered to a female baboon and brain images were obtained using a Siemens ECAT EXACT scanner for determination of brain regional uptake and blood-brain barrier permeability.
At 30 min postinjection, [11C]MTICU remained 64% intact in vivo and 95% intact in vitro. Lipophilicity estimation gave Log p = 1.08 +/- 0.08 (n = 6). The brain (0.11% ID/g)-to-blood (0.20% ID/g) ratio was 1:2 at 30 min postinjection. Uptake in the cerebellum was 20% higher than in either the cortex or the brain stem (p < 0.05). Blockage using 1 mg/kg MTICU reduced uptake in the cerebellum and the cortex by 22%, but did not affect the brain stem. PET imaging showed that [11C]MTICU brain uptake, corrected for blood volume, was stable from 10 min to 1 hr at approximately 0.4% ID/organ. PET images of a baboon brain showed increased uptake in the region of the olfactory bulb compared to uniform biodistribution in the rest of the brain.
The [11C]MTICU is a tracer that is potentially useful in determining nNOS levels in vivo.
Journal of Nuclear Medicine 08/1997; 38(8):1273-8. · 6.38 Impact Factor
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ABSTRACT: Excess nitric oxide has been implicated in the pathogenosis of experimental autoimmune encephalomyelitis (EAE) which is an animal model for multiple sclerosis. Positron emission tomography (PET) is an imaging technique that has shown utility for studying enzyme systems in vivo. A positron-labeled inducible nitric oxide synthetase (iNOS) inhibitor has been studied in EAE-affected mice as well as controls. Greater uptake of the radiolabeled inhibitor was observed in the spinal cord of the affected mice than of control mice. Increased uptake was also observed in other organs not previously implicated in this experimental model. The increased uptake of the radiopharmaceutical in this model suggests that this tracer may have the potential for measuring increased levels of iNOS in humans by PET.
Nitric Oxide 07/1997; 1(3):263-7. · 3.55 Impact Factor
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ABSTRACT: The labeled serotonin agonist 3-[18F]fluoro-N-(alpha,alpha,alpha-trifluoro-m-tolyl)piperazine (18FTFMPP) was prepared rapidly using the labeling procedure for trifluorotoluenes, [18F]fluoro-for-nitro exchange, followed by an alumina-supported bis-alkylation. After normal-phase HPLC purification, the labeled product was obtained in 20-32% (n = 20) decay-corrected radiochemical yield with a radiochemical purity > 98% and a specific activity of 100 GBq/mumol. The synthesis time including purification was 3 h. The receptor binding affinity of FTFMPP to rat brain membranes was found to be similar to that of the nonfluorinated parent compound (TFMPP). Although TFMPP has been proposed by others as an agent for the imaging of serotonin receptors, only minimal receptor-mediated uptake was observed.
Nuclear Medicine and Biology 04/1997; 24(3):269-73. · 3.02 Impact Factor
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ABSTRACT: In an effort to develop a tracer for probing inducible nitric oxide synthase (iNOS) levels in vivo utilizing positron emission tomography, we have synthesized and evaluated two positron-emitting iNOS selective inhibitors: S-[11C]methylisothiourea (1b) and S-(2-[18F]fluoroethyl)-isothiourea (3b). Prior to fluorine-18 labeling, the nonradioactive fluoro derivative S-(2-fluoroethyl)isothiourea (3a) was prepared and determined to have a 9-fold higher selectivity for iNOS compared to endothelial NOS (eNOS). Radiochemical synthesis of both compounds, in high radiochemical purity and at high specific activity, was accomplished by the S-alkylation reaction of labeled precursors (11CH3I or 18FCH2CH2OTf) with thiourea. An in vitro model, J774 macrophage cell line, was used to assess the uptake of radiolabeled iNOS inhibitor in response to iNOS induction at the cellular level. Increased cell uptake of these two labeled compounds at stimulated iNOS levels, as well as blocking under controlled in vitro conditions, was observed. Lipophilicity (log P o/w), stability, and tissue biodistribution data of both compounds are reported. Serum stability studies indicate that 3b metabolized much more rapidly compared to the relatively stable 1b in vitro and in vivo. Based on in vitro cell uptake data, both tracers were further evaluated in lipopolysaccharide (LPS)-pretreated rats. LPS has been reported to induce iNOS protein expression in the liver, lung, heart, and kidney and other tissues. The uptake for LPS-pretreated rats (6 h post-treatment) was significantly increased in the liver, kidney, and heart for 3b at 10 min and in the liver and lung for 1b at 30 min. The results suggest that this first generation of radiolabeled inhibitors may be useful for assessing induction of iNOS in vivo with PET.
Journal of Medicinal Chemistry 01/1997; 39(26):5110-8. · 5.25 Impact Factor
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ABSTRACT: Using positron emission tomography (PET) and nitric oxide radiolabeled with nitrogen-13 (half-life 9.97 min) we probed the distribution and kinetics of inhaled nitric oxide in anesthetized dogs. The washout of this gas after inhalation was much slower than that observed for [13N]nitrogen gas, demonstrating its uptake by lung tissue. The small fraction of radioactivity found in the plasma was determined to be in the form of [13N]nitrate. The administered gas contained < 1 ppm of nonradioactive nitric oxide, which is believed to be below the physiologic threshold for vasorelaxation.
Nuclear Medicine and Biology 08/1996; 23(6):773-7. · 3.02 Impact Factor
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ABSTRACT: The present study examined the effects of 6 wk of ovarian endocrine deficiency on skeletal muscle GLUT-4 glucose transporter protein and glucose transport activity in sedentary and endurance-trained rats. Female Wistar rats (10 wk old) underwent bilateral ovariectomy (OVX) or sham surgery followed by a 5-wk swim-training protocol. OVX resulted in no significant changes in glycogen or GLUT-4 glucose transporter concentration in the soleus, epitrochlearis, or flexor digitorum brevis (FDB) muscles or in basal and maximally insulin-stimulated 2-deoxy-D-[1,2-3H]glucose (2-[3H]DG) transport in the soleus or epitrochlearis, suggesting that moderate-duration ovarian hormone deficiency does not significantly impair insulin action in skeletal muscle. In contrast, OVX decreased the maximal activation of 2-[3H]DG transport in the FDB by in vitro electrical stimulation. OVX had no significant effect on the training-induced changes in oxidative enzyme activities, GLUT-4 protein expression, glycogen content, or insulin-stimulated 2-[3H]DG transport in the soleus or epitrochlearis. These findings provide the first evidence that ovarian hormone deficiency decreases contraction-stimulated glucose transport in skeletal muscle.
Journal of Applied Physiology 06/1996; 80(5):1605-11. · 3.75 Impact Factor
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ABSTRACT: We developed a procedure for measuring pulmonary angiotensin-converting enzyme kinetics with fluorine-18 fluorocaptopril and positron emission tomography (PET). The method is based on the application of a compartmental receptor model that represents the kinetics of two species of ligand, presumably the trans and cis conformers of captopril. The input function was characterized and includes corrections for the labeled metabolites of fluorocaptopril. Application of the procedure to lung time-activity data obtained with PET produced estimates of kinetic parameters demonstrating fast kinetics for one conformer and slower kinetics for the other. Simulation studies were performed to evaluate the sensitivity of the estimated parameters to errors in the model assumptions and in measured values for variables required for analysis of the PET data. Estimates for two of the kinetic parameters, the amount of perfused unbound functional enzyme normalized to regional lung volume and the association rate constant for the trans conformer, were relatively stable even with large errors in the input data, varying < 30% from true values for all perturbations. Thus, the procedure produces reliable estimates of the kinetics of the trans conformer of captopril as well as theoretical curves that are close to the observed data.
Journal of Applied Physiology 03/1995; 78(3):1158-68. · 3.75 Impact Factor
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ABSTRACT: We measured pulmonary angiotensin-converting enzyme (ACE) kinetics with fluorine-18 captopril and positron emission tomographic (PET) imaging in five control dogs and in five dogs after 20-30 min of left caudal lobe (LCL) hypoxic ventilation. Time-activity data obtained with PET were interpreted with a compartmental receptor model relating changes in tissue and blood activity to one another within the region. In control dogs, the mean ratio of regional blood flow (measured by PET) between left and right dorsal lung regions was 0.90 +/- 0.16 (SD) vs. 0.54 +/- 0.24 (P < 0.05) in LCL hypoxic dogs. In control dogs, the amount of perfused unbound enzyme normalized to regional extravascular water concentration (Bmax/EVLW) averaged 13.3 +/- 8.9 x 10(-6) mmol ACE/ml EVLW; the ratio of regional values between the left and right sides was 1.02 +/- 0.18. In the LCL hypoxic dogs, Bmax/EVLW was 9.7 +/- 11.3 x 10(-6) mmol/ml hypoxic lung region and the ratio was 0.47 +/- 0.31 (P < 0.05). In control dogs, the coefficient of variation for Bmax/EVLW among regions was only 19 +/- 10%, although the between-dog variation was greater (64 +/- 4%). We conclude that this completely noninvasive method appears to be a promising approach for evaluating the expression of pulmonary ACE in vivo.
Journal of Applied Physiology 03/1995; 78(3):1169-78. · 3.75 Impact Factor
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ABSTRACT: There are several reports in the literature on the evaluation of chelates containing two nitrogens and two sulfurs (N2S2) as four coordinate ligands (in solution) for gallium and indium radiopharmaceuticals. No thermodynamic stability constants of these ligands were reported, and the stability of these complexes in vivo has been questioned. L,L-Ethylenedicysteine (EC) is a N2S2 ligand that also contains two carboxylic acid moieties for complexation of Ga(III) and In(III) in a hexacoordinate environment. The stability constants of Ga- and In-EC have been determined by potentiometric methods. The stability of In-EC was found to be greater than that of Ga-EC, with stability constants (log K's) of 33.0 and 31.5, respectively. A molecular mechanics evaluation of the Ga- and In-EC complexes support the thermodynamic results. 67Ga- and 111In-labeled complexes of EC were prepared and analyzed by thin layer chromatography and electrophoresis. Both complexes were evaluated in biodistribution studies in normal Sprague-Dawley rats. 111In-EC cleared rapidly through the hepatobiliary system, whereas 67Ga-EC remained in the liver at 1 h post-injection. Although 67Ga-EC was retained in the liver, suggesting instability of the complex in vivo. 67Ga-EC was stable in rat plasma in vivo at 2 h post-injection. Because of the high thermodynamic and in vivo stability of In-EC, derivatives of EC may have applications as bifunctional chelates for 111In-labeled proteins and peptides. More lipophilic analogues of 68Ga-EC may also have potential as myocardial PET imaging agents.
Nuclear Medicine and Biology 03/1995; 22(2):165-73. · 3.02 Impact Factor
