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M J Welch

Publications and source records attributed to M J Welch.

At least 37 records · Page 2Linked to original sources
PubMed2000

High-resolution microPET imaging of carcinoembryonic antigen-positive xenografts by using a copper-64-labeled engineered antibody fragment.

Rapid imaging by antitumor antibodies has been limited by the prolonged targeting kinetics and clearance of labeled whole antibodies. Genetically engineered fragments with rapid access and high retention in tumor tissue combined with rapid blood clearance are suitable for labeling with short-lived radionuclides, including positron-emitting isotopes for positron-emission tomography (PET). An engineered fragment was developed from the high-affinity anticarcinoembryonic antigen (CEA) monoclonal antibody T84.66. This single-chain variable fragment (Fv)-C(H)3, or minibody, was produced as a bivalent 80 kDa dimer. The macrocyclic chelating agent 1,4,7, 10-tetraazacyclododecane-N,N',N", N"'-tetraacetic acid (DOTA) was conjugated to the anti-CEA minibody for labeling with copper-64, a positron-emitting radionuclide (t(1/2) = 12.7 h). In vivo distribution was evaluated in athymic mice bearing paired LS174T human colon carcinoma (CEA positive) and C6 rat glioma (CEA negative) xenografts. Five hours after injection with (64)Cu-DOTA-minibody, microPET imaging showed high uptake in CEA-positive tumor (17.9% injected dose per gram +/- 3.79) compared with control tumor (6.0% injected dose per gram +/- 1.0). In addition, significant uptake was seen in liver, with low uptake in other tissues. Average target/background ratios relative to neighboring tissue were 3-4:1. Engineered antibody fragments labeled with positron-emitting isotopes such as copper-64 provide a new class of agents for PET imaging of tumors.

Animals↗
PubMed2000

Synthesis and characterization of racemic mixture and meso isomers of bis(trans-2-aminocyclohexyl)aminepentaacetic acid and the stabilities of their Gd(III) complexes.

The synthesis and characterization of two multidentate ligands, the racemic mixture and meso isomers of bis-(trans-2-aminocyclohexyl)aminepentaacetic acid, are described. Equilibrium constants for their Gd(III) complexes were determined by direct potentiometry. The formation constants (KML = [ML]/[M][L]) of Gd(III)-Cycyracemic in 0.10 M KCl at 25.0 degrees C is 10(20.71; that for the meso isomer is 10(20.42). The crystal structure of (1S,2S,1'S,2'S)-bis(trans-2-aminocyclohexyl)amine-N,N,N',N",N"-pentaacetic acid, penta-tert-butyl ester (C42H75N3O10), is reported. This compound crystallizes in the triclinic system with space group P1 with cell parameters a = 10.805(2) A, b = 11.382(2) A, c = 20.999(4) A, alpha = 91.41(3) degrees, beta = 98.23(3) degrees, gamma = 113.88(3) degrees, V = 2327.8(8) A3, Z = 2, Dx = 1.116 g mL-1. The results are compared to the crystal structures of the gadolinium complexes and the predictions derived from molecular mechanics.

Algorithms↗
PubMed2000

Characterization of prenylated xanthones and flavanones by liquid chromatography/atmospheric pressure chemical ionization mass spectrometry.

Reversed-phase liquid chromatography with atmospheric pressure chemical ionization mass spectrometry (LC/APCI-MS) in the positive-ion mode was utilized to analyze crude ether extracts from the root bark of Maclura pomifera, a tree known to have a high content of prenylated xanthones and flavanones. Identification of three xanthones and two flavanones was based on their unique mass spectra. Under optimum conditions peaks corresponding to the [MH](+) ion and characteristic fragments for each compound were observed. (1)H NMR data were used to confirm the identities of two xanthones that had the same molecular mass and similar fragmentation patterns. Fragmentation of the analytes was achieved by application of an electrostatic potential at the entrance of the single quadrupole mass spectrometer. The optimum voltage for fragmentation was found to be related to the class of compounds analyzed and, within each class, to be dependent on the structure of the prenyl moiety. Collision-induced pathways consistent with precedent literature describing the MS characterization of similar compounds and with the observed fragmentation patterns are tentatively proposed.

Chromatography, Liquid↗
PubMed2000

Evaluation of 62Cu labeled diacetyl-bis(N4-methylthiosemicarbazone) as a hypoxic tissue tracer in patients with lung cancer.

62Cu labeled diacetyl-bis(N4-methylthiosemicarbazone) (62Cu-ATSM) has been proposed as a generator-produced, positron-emitting tracer for hypoxic tissue imaging. From basic studies, the retention mechanism of 62Cu-ATSM is considered to be closely related to cytosolic/microsomal bioreduction, a possible system for hypoxic bioreductive drug activation. In order to evaluate the characteristics of 62Cu-ATSM, PET studies were performed in 4 normal subjects and 6 patients with lung cancer. 62Cu-ATSM cleared rapidly from the blood with little lung uptake (0.43+/-0.09, uptake ratio; divided by the arterial input function) in normal subjects. Intense tumor uptake of 62Cu-ATSM was observed in all patients with lung cancer (3.00+/-1.50). A negative correlation was observed between blood flow and flow-normalized 62Cu-ATSM uptake in three of four patients. In contrast, 62Cu-ATSM uptake was not related to that of 18F-fluorodeoxyglucose. The negative correlation between blood flow and flow normalized 62Cu-ATSM uptake suggests an enhancement of retention of 62Cu-ATSM by low flow. 62Cu-ATSM is a promising PET tracer for tumor imaging, which might bring new information for chemotherapeutic treatment as well as radiotherapy of hypoxic tumors.

Adenocarcinoma↗
PubMed2000

Exhaled nitric oxide correlates with experimental lung transplant rejection.

BACKGROUND: 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. METHODS: 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. RESULTS: 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. CONCLUSIONS: 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.

Acute Disease↗
PubMed2000

Sensitivity of embryonic rat dorsal root ganglia neurons to Clostridium botulinum neurotoxins.

Clostridium botulinum neurotoxins (BoNT) are zinc dependent endopeptidases which, once internalised into the neuronal cytosol, block neurotransmission by proteolysis of membrane-associated proteins putatively involved in synaptic vesicle docking and fusion with the plasma membrane. Although many studies have used a variety of cellular systems to study the neurotoxins, most require relatively large amounts of toxin or permeabilisation to internalise the neurotoxin. We present here a primary culture of embryonic rat dorsal root ganglia (DRG) neurons that exhibits calcium-dependent substance P secretion when depolarised with elevated extracellular potassium and is naturally BoNT sensitive. The DRG neurons showed a different IC50 for each of the toxins tested with a 1000 fold difference between the most and least potent neurotoxins (0.05, 0.3, 30 and approximately 60 nM for A, C, F and B, respectively). BoNT/A cleavage of SNAP-25 was seen as early as 2 h, but substance P secretion was not significantly inhibited until 4 h intoxication and the effects of BoNT/A were observed for as long as 15 days. This primary neuronal culture system represents a new and sensitive cellular model for the in vitro study of the botulinum neurotoxins.

Animals↗
PubMed2000

Radiochemical synthesis and tissue distribution of Tc-99m-labeled 7alpha-substituted estradiol complexes.

The diagnosis and staging of breast cancer could be improved by the development of radiopharmaceutical imaging agents that provide a noninvasive determination of the estrogen receptor (ER) status of tumor cells. Agents labeled with (99m)Tc would be especially valuable in this regard. In attempting to achieve this goal, we synthesized four (99m)Tc-labeled 7alpha-substituted estradiol complexes. One complex utilizes the "3+1" mixed ligand design to introduce the Tc metal, whereas the other three took advantage of the cyclopentadienyltricarbonylmetal (CpTM) design. The Tc moieties were attached to the 7alpha position of estradiol with a hexyl tether, a monoether tether, or a polyether tether. The corresponding rhenium compounds have binding affinities for the ER of 20-45% compared with estradiol. Radiochemical yields of the (99m)Tc-labeled compounds ranged from approximately 15% for the CpT-Tc complexes to 95% for the 3 + 1 inorganic complex. Tissue distribution studies in immature female rats showed low nonreceptor-mediated uptake in the target organs and high uptake in nontarget organs such as the liver and fat. These complexes represent the first time that estradiol has been labeled at the 7alpha position with (99m)Tc and provide a further refinement of our understanding of ligand structure-binding affinity correlations for the ER.

Animals↗
PubMed2000

Labeling and in vivo evaluation of novel copper(II) dioxotetraazamacrocyclic complexes.

64Cu shows promise as both a positron emission tomography imaging and radiotherapeutic radionuclide due to its half-life (T(1/2) = 12. 7 h), decay characteristics (beta(+) [19%]; beta(-) [40%]), and the capability to produce it on a large-scale with high specific activity on a biomedical cyclotron. Macrocyclic chelators are generally used as bifunctional chelators to attach Cu(II) to antibodies and peptides due to their relatively high in vitro stability. To investigate neutral Cu(II) complexes, we performed labeling experiments with six tetraazamacrocyclic ligands with different chelate ring sizes. 1,4,8,11-Tetraazacyclotetradecane-3, 9-dione (1), 1,4,8,11-tetraazacyclotetradecane-5,7-dione (2), 1,4,7, 10-tetraazacyclotridecane-11,13-dione (3), 1,4,7, 10-tetraazacyclotridecane-2,9-dione (4), 1,4,7, 10-tetraazacyclododecane-2,9-dione (5), and 1,4,7, 10-tetraazacyclotridecane-3,8-dione (6) were radiolabeled with (64)Cu. Only (64)Cu-labeled 1 readily formed a complex in high purity, and therefore was evaluated in vivo. The rapid blood, liver, and kidney clearance of (64)Cu-labeled 1 suggest that ligand 1 may be useful as a macrocyclic structure to design new bifunctional chelators for copper radionuclides in diagnostic or radiotherapeutic studies and is a potential alternative to currently used macrocyclic bifunctional chelators.

Animals↗
PubMed2000

Novel gallium(III) complexes transported by MDR1 P-glycoprotein: potential PET imaging agents for probing P-glycoprotein-mediated transport activity in vivo.

BACKGROUND: Multidrug resistance (MDR) mediated by expression of MDR1 P-glycoprotein (Pgp) represents one of the best characterized barriers to chemotherapy in cancer patients. Positron emission tomography (PET) agents for analysis of Pgp-mediated drug transport activity in vivo would enable noninvasive assessment of chemotherapeutic regimens and MDR gene therapy. RESULTS: Candidate Schiff-base phenolic gallium(III) complexes were synthesized from their heptadentate precursors and gallium(III)acetylacetonate. Crystal structures demonstrated a hexacoordinated central gallium with overall trans-pseudo-octahedral geometry. Radiolabeled (67)Ga-complexes were obtained in high purity and screened in drug-sensitive (Pgp(-)) and MDR (Pgp(+)) tumor cells. Compared with control, lead compound 6. demonstrated antagonist-reversible 55-fold lower accumulation in Pgp-expressing MDR cells. Futhermore, compared with wild-type control, quantitative pharmacokinetic analysis showed markedly increased penetration and retention of 6. in brain and liver tissues of mdr1a/b((-/-)) gene disrupted mice, correctly mapping Pgp-mediated transport activity at the capillary blood-brain barrier and hepatocellular biliary cannalicular surface in vivo. CONCLUSIONS: These results indicate that gallium(III) complex 6. is recognized by MDR1 Pgp as an avid transport substrate, thereby providing a useful scaffold to generate (68)Ga radiopharmaceuticals for molecular imaging of Pgp transport activity in tumors and tissues in vivo using PET.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed2000

Low-dose inhaled fluticasone propionate versus oral zafirlukast in the treatment of persistent asthma.

BACKGROUND: Few studies have compared the efficacy of inhaled corticosteroids and leukotriene modifiers for the treatment of persistent asthma. OBJECTIVE: Our purpose was to compare the efficacy of a low dose of inhaled fluticasone propionate (FP) with that of oral zafirlukast in the treatment of persistent asthma previously treated with short-acting beta(2)-agonists alone. METHODS: A 12-week, randomized, double-blind, double-dummy, multicenter study was conducted in 451 patients aged 12 years and older with asthma who were symptomatic on short-acting beta(2)-agonists alone. After an 8- to 14-day run-in period, patients were randomized to treatment with FP 88 microg twice daily or zafirlukast 20 mg twice daily. RESULTS: Treatment with FP was more effective than treatment with zafirlukast in increasing morning FEV(1) (by 0.42 L vs 0.20 L over baseline, P <.001), morning peak expiratory flow (by 49.94 L/min vs 11.68 L/min over baseline, P <. 001), and evening PEF (by 38.91 L/min vs 10.50 L/min over baseline, P <.001). Statistically significant differences between the two treatments in FEV(1) were noted after the first observation (week 4) and in morning and evening peak expiratory flow by week 2. Mean change in percentage of symptom-free days was greater with FP than with zafirlukast (28.5% of days vs 15.6% of days, P <.001) and FP significantly increased the percentage of rescue-free days by 40.4% of days compared with 24.2% of days with zafirlukast (P <.001). Treatment with FP significantly reduced albuterol use by 2.39 puffs per day compared with 1.45 puffs per day (P <.001) and increased the percentage of nights with no awakenings by 21.2% of nights compared with 8.0% of nights with zafirlukast (P <.001). CONCLUSION: The clinical effectiveness of a low dose of FP as first-line therapy in patients with persistent asthma who are symptomatic on beta(2)-agonists alone is superior to that of zafirlukast.

Administration, Inhalation↗
PubMed2000

Challenges in evaluating controller asthma therapy in children.

Clinical data about the efficacy and safety of controller medications for pediatric patients of all ages are limited, especially when compared with the amount of data available for medications for adults. The considerable data collected so far in adults about these therapeutic agents need to be confirmed in children because pharmacologic profiles will not necessarily be the same for children. Clinical research studies need to include younger populations so that the necessary information can be available for physicians who want to use controller therapy for their pediatric patients. Special challenges confront the pharmaceutical companies and the research investigators who undertake these clinical studies, but such challenges are surmountable.

Adrenal Cortex Hormones↗
PubMed2000

Determination of 11-nor-delta9-tetrahydrocannabinol-9-carboxylic acid in a urine-based standard reference material by isotope-dilution liquid chromatography-mass spectrometry with electrospray ionization.

A new method is presented for the determination of 11-nor-delta9-tetrahydrocannabinol-9-carboxylic acid (THC-9-COOH) in urine-based standard reference materials (SRMs) for marijuana metabolite. This method is based on isotope-dilution liquid chromatography-mass spectrometry (LC-MS) using electrospray for ionization (ESI). An isotopically labeled compound, 5',11-nor-delta9-THC-9-carboxylic acid-d3, was used as an internal standard. Solid-phase extraction (SPE) was used to prepare samples for LC-MS analyses. LC was performed on a C18 column with an isocratic mobile phase consisting of 0.05 M of ammonium acetate in methanol/water (75:25). Electrospray ionization in the negative ion mode was used to monitor the [M-H]- ions at m/z 343 and 346 for THC-9-COOH and its labeled internal standard, respectively. Samples of SRM 1507b (THC-9-COOH in freeze-dried urine) were prepared and measured on three separate sets. The within-set coefficients of variation ranged from 0.32% to 2.77%. The correlation coefficients of the regression lines were 0.999 to 1.000. The detection limit for THC-9-COOH with this method is estimated to be 5 pg/mL. This method compared well with the gas chromatography-mass spectrometry method used for certification, and results were within the certified values of THC-9-COOH for SRM 1507b.

Chromatography, Liquid↗
PubMed1999

Cytosolic/microsomal redox pathway: a reductive retention mechanism of a PET-oncology tracer, cu-pyruvaldehyde-bis(N4-methylthiosemicarbazone) (cu-PTSM).

OBJECTIVE: To clarify the retention mechanism of a PET imaging agent Cu-pyruvaldehyde-bis(N4-methylthiosemicarbazone) (Cu-62-PTSM) in tumor cells, reductive metabolism of non-radioactive Cu-PTSM in five cultured tumor cell lines, a tumor specimen and non-tumor tissues in vitro was evaluated by electron spin resonance spectrometry (ESR). RESULTS: In the brain, mitochondrial electron transport enzyme reduced Cu-PTSM specifically. On the other hand, Cu-PTSM was not reduced in tumor mitochondria. The mitochondrial electron transport enzyme in tumor cells was not damaged, but NADH was considered to be depleted. In compensation for that, the tumor cells acquired complementary reduction activity in the microsome/cytosol. The reduction was enzymatic and NADH-dependent, possibly similar to the activation mechanism of bioreductive anticancer drugs. CONCLUSION: Cu-PTSM and its derivatives are considered to be used as a marker for microsome/cytosol redox ability in PET oncology, although the physiological role of the redox enzyme system in tumor cells has not been clarified. The change in electron (NADH) flow in tumor cells might be a mechanism supporting aerobic glycolysis in tumor cells.

Animals↗
PubMed1999

Positron emission tomographic assessment of "metabolic flare" to predict response of metastatic breast cancer to antiestrogen therapy.

We have investigated whether increased tumor uptake of fluorine-18 fluorodeoxyglucose (FDG) detected with positron emission tomography (PET) early after initiating tamoxifen therapy ("metabolic flare") predicts a hormonally responsive breast cancer. Eleven postmenopausal women with biopsy-proved estrogen receptor-positive (ER+) metastatic breast cancer were studied by PET with FDG and 16alpha[18F]fluoro-17beta-estradiol (FES) before and 7-10 days after initiation of tamoxifen therapy. FDG and FES uptake was evaluated semiquantitatively in 21 lesions. The PET results were correlated with follow-up evaluation, continued until the patient became unresponsive to hormone therapy (3-24 months). There were seven responders and four nonresponders based on clinical follow-up. None of the responders had a clinical flare reaction, but all demonstrated metabolic flare, with a mean +/- standard deviation increase in tumor standardized uptake value (SUV) for FDG of 1.4+/-0. 7. No evidence for flare was noted in the nonresponders (change in SUV for FDG -0.1+/-0.4; P = 0.008 vs. responders). The degree of ER blockade by tamoxifen was greater in responders (mean decrease in SUV 2.7+/-1.7) than in nonresponders (mean decrease 0.8+/-0.5) (P = 0.04). The lesions of responders had higher baseline SUVs for FES than did those of three of four nonresponders (>/=2.2 vs </=1.7). The findings of a metabolic flare by FDG-PET and the degree of ER blockade by FES-PET early after institution of tamoxifen treatment appear to predict responsiveness to antiestrogen therapy in patients with ER+ metastatic breast cancer.

Antineoplastic Agents, Hormonal↗
PubMed1999

Comparative studies of Cu-64-ATSM and C-11-acetate in an acute myocardial infarction model: ex vivo imaging of hypoxia in rats.

Copper labeled diacetyl-bis(N4-methylthiosemicarbazone) (Cu-ATSM) is a promising agent for the imaging of hypoxic tissues. In the present study 64Cu(t1/2 = 12.8 h) labeled Cu-ATSM was used in combination with 11C (t1/2 = 20.3 min) labeled acetate as a regional perfusion marker to visualize hypoxic rat heart tissue in an acute left anterior descending (LAD) coronary artery occluded rat model using an ex vivo tissue slice imaging technique. 64Cu-ATSM was injected intravenously c.a. 10 min after occlusion and rats were sacrificed by cervical dislocation 10 min after injection. Carbon-11-acetate was injected 1 min before sacrifice to obtain a measure of blood flow. The heart was dissected, frozen, and cut into 1-mm thick slices with a gauged slicer, and 11C images were obtained with an electronic autoradiography instrument. After decay of 11C, 64Cu images were obtained in the same manner. In ischemic regions, where there was low 11C accumulation, 64Cu showed high accumulation when compared with normal regions. In rats with a large occlusion, the center of the ischemia did not show any accumulation of either 11C or 64Cu, indicating no blood supply. Cu-ATSM appears to be useful for the detection of hypoxia with contrast being observed at short times (10 min) postinjection.

Acetates↗