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David J Stewart

Publications and source records attributed to David J Stewart.

13 recordsLinked to original sources
PubMed2006

Chlorine dioxide oxidation of guanosine 5'-monophosphate.

The reactions between aqueous ClO2 and guanosine 5'-monophosphate (5'-GMP) are investigated from pH 5.96 to 8.30. The decay of ClO2 follows mixed first-order and second-order kinetics. The addition of chlorite (0.01-0.05 M) to the reaction mixture suppresses the reaction rate and changes the observed decay of ClO2 to second-order. The reaction rates increase greatly with pH to give oxidized products. The second-order rate constant for the guanosine anion is 4.7 x 10(5 )M-1 s-1 and comprises a mixture of rate constants, k1k2/k-1. The ratio k1/k-1, with a calculated value of 2.4 x 10(-4), corresponds to the reversible reaction between ClO2 and the guanosine anion to generate ClO2- and the guanosyl radical. To determine k1/k-1 and k2, E values for guanosine and ClO2 are used as well as acid dissociation constants for guanosine and its radical. The value of k1 (1.1 x 10(5) M-1 s-1) represents the reaction between ClO2 and the guanosine anion as determined by initial rates. The second-order rate constant k2, with a value of 1.8 x 10(9 )M-1 s-1, represents the reaction between the guanosyl radical with a second molecule of ClO2 to generate a guanosyl-OClO adduct. The consumption of two mol of ClO2 per mol of 5'-GMP corresponds to a four-electron oxidation that gives ClO(2- )in the first step and HOCl in the second step. The 2',3',5'-tri-O-acetylated derivative of guanosine is used to more easily separate guanosine from its ClO2 oxidation products. Imidazolone and monochlorinated imidazolone are identified as products of the reaction between ClO2 and guanosine.

Chlorine Compounds↗
PubMed2005

Imaging of the patient with non-small cell lung cancer.

Lung cancer is the most common type of cancer and is the leading cause of cancer deaths in the United States for both men and women. Even though the 5-year survival rate of patients with lung cancer remains dismal at 14% for all cancer stages, treatments are improving and newer agents for lung cancer appear promising. Therefore, an accurate assessment of the extent of disease is critical to determine whether the patient is treated with surgical resection, radiation therapy, chemotherapy, or a combination of these modalities. Radiologic imaging plays an important role in the staging evaluation of the patient; however, radiologists need to be aware that there are also important differences in what each specialist needs from imaging to provide appropriate treatment. This article reviews the role of imaging in patients with non-small cell lung cancer, with an emphasis on the radiologic imaging findings relevant for each specialty.

Carcinoma, Non-Small-Cell Lung↗
PubMed2005

Disodium Ascorbyl Phytostanyl Phosphates (FM-VP4) reduces plasma cholesterol concentration, body weight and abdominal fat gain within a dietary-induced obese mouse model.

PURPOSE: The purpose of this study was to determine if Disodium Ascorbyl Phytostanol Phosphates (FM-VP4) alters animal body weight and plasma lipid levels in a dietary-induced obese mouse model. METHODS: Twenty-four C57BL6 mice (28 days old) were housed individually and fed a standard mouse diet for 2 weeks upon arrival. After 2 weeks the animals were weighed and divided in 4 groups of similar average weight, and the groups received a low fat (10% kcal from fat) and high fat (45% kcal from fat) diet with or without FM-VP4 (2% w/w) for 12 continuous weeks. Food, water and caloric intake and body weight were recorded on a daily basis throughout the duration of the study. Following the 12th week of the study all animals were humanely sacrificed and blood and abdominal fat pads were harvested for further analysis. Plasma cholesterol, triglyceride, AST/ALT and creatinine levels were measured using enzymatic kits. RESULTS: There is a significant difference in weight gain between the low-fat diet and the low-fat diet + 2% w/w FM-VP4 treatment groups (P<0.05), as well as between the high-fat diet and the high-fat diet + 2% w/w FM-VP4 treatment groups (P<0.05). However, the reduction of weight gain of the high-fat diet + 2% FM-VP4 treatment group compared to the high-fat group was 51%, while the reduction in weight gain between the low-fat diet + 2% w/w FM-VP4 treatment group and the low-fat diet group was 17% over the duration of the study. No significant differences in food and water intakes, serum creatinine and AST/ALT levels were observed between the four groups. No significant differences in caloric intake between the low-fat diet and the low-fat diet + 2% w/w FM-VP4. However, a significant difference in caloric intake between high-fat diet and the high-fat diet + 2% w/w FM-VP4 treatment groups was observed. In addition, significant reductions in plasma cholesterol levels and abdominal fat pad weight between diet alone and diet + FM-VP4 treatment groups were observed. CONCLUSIONS: These findings suggest that FM-VP4 may have potential weight-loss and cholesterol lowering activity in both High Fat and Low Fat Diets treated groups.

Abdominal Fat↗
PubMed2005

The effect of intra-articular methadone on postoperative pain following anterior cruciate ligament reconstruction.

BACKGROUND: Intra-articular narcotics have proven efficacy for providing pain relief following knee arthroscopy. This effect is short-lived. Methadone, with its long serum half-life (thirty-five hours, compared with two hours for morphine) could provide improved and prolonged pain relief. The purpose of the present study was to examine the effects of an intra-articular injection of methadone on postoperative analgesia following arthroscopic anterior cruciate ligament reconstruction. METHODS: Sixty-five skeletally mature patients undergoing primary anterior cruciate ligament reconstruction were randomly assigned to one of three groups, all of which received an intra-articular injection consisting of 9.5 mL of 0.5% bupivacaine with 1:200,000 epinephrine at the completion of the procedure. In addition, the remaining 0.5 mL of the syringe was filled with one of three substances. The study group (twenty-five patients) received 5 mg of methadone, the comparison group (twenty-one patients) received 5 mg of morphine, and the control group (nineteen patients) received 0.5 mL of saline solution. All supplemental pain medications were given on an as-needed basis, recorded, and converted to morphine equivalents. Specific variables that were measured included supplemental analgesia requirements during both the inpatient period and the outpatient period (from the time of discharge to the seventh postoperative day) and pain scores. RESULTS: There was no significant difference in inpatient (p = 0.998) or outpatient (p = 0.887) supplemental analgesic requirements or pain scores between the methadone group (Group 1) and the control group (Group 3). The morphine group (Group 2) required significantly less inpatient (p = 0.014) and outpatient (p = 0.044) supplemental analgesia compared with the control group (Group 3). There were no complications. CONCLUSIONS: The present report represents the first known study of the use of intra-articular methadone and establishes that this analgesic is safe at a single dose of 5 mg. At this dose, however, methadone does not provide improved postoperative analgesia following arthroscopic anterior cruciate ligament reconstruction. In contrast, intra-articular morphine does appear to be effective for decreasing postoperative pain.

Adult↗
PubMed2004

Phase II study of alternating chemotherapy regimens for advanced non-small cell lung cancer.

PURPOSE: We assessed the use of alternating drugs with differing mechanisms of action as treatment for advanced non-small cell lung cancer. BACKGROUND: We hypothesized that the shape of a dose-response curve would be determined by the major mechanisms of resistance of a cancer to the drug being studied. Assessment of data from published clinical trials suggested that if our hypothesis were correct resistance of non-small cell lung cancer to most agents is due to "saturable passive" resistance mechanisms (non-competitive inhibition of drug effect due to deficiency of a factor required for drug effect) rather than to "active" resistance mechanisms (competitive inhibition of drug effect due to excess of a factor) or to "non-saturable passive resistance (due to factor alteration or mutation). Using drugs with differing mechanisms of action is a strategy that might be of value against passive resistance. METHOD: In patients with advanced non-small cell lung cancer, we used four alternating cisplatin-based regimens. In each regimen, cisplatin 80 mg/m(2) was given iv on day 1 of each course. The regimens were: cisplatin + vinorelbine 25 mg/m(2) days 1, 8 and 15, cisplatin + gemcitabine 1000 mg/m(2) days 1, 8 and 15, cisplatin + paclitaxel 200 mg/m(2) day 1 iv over 1h, and cisplatin + etoposide 100 mg/m(2) po days 1-6. Patients were assigned randomly to different regimen sequences. Patients first received 1 course of each of these 4 regimens, then received 1 further course of each of single agent vinorelbine, gemcitabine, paclitaxel and etoposide (at the same doses as in courses 1-4), without cisplatin. (Cisplatin was omitted from courses 5-8 to limit cumulative toxicity.) Change in tumor size was measured after each course. RESULTS: Thirty-six patients were entered. One patient achieved complete remission and nine achieved partial remissions, for an objective response rate of 28% (95% confidence intervals, 13-43%). Nineteen patients (53%) (95% confidence intervals, 37-69%) had stable disease. Eleven patients had growth of >10% on one regimen followed by tumor shrinkage of >10% on a later one. Median survival was 8.1 months, 1-year survival was 28% and 2-year survival was 6%. No unexpected toxicity was seen. CONCLUSIONS: The use of four alternating regimens is feasible in advanced non-small cell lung cancer. Response rates and survival times were comparable to those observed for standard chemotherapy approaches, suggesting that this strategy does not offer any major advantage. We plan to explore the hypothesis that this approach failed since tumor cells surviving first exposure to chemotherapy rapidly down-regulate their ability to undergo apoptosis.

Administration, Oral↗
PubMed2004

Recovery of Mycobacterium avium subspecies paratuberculosis from the natural host for the extraction and analysis in vivo-derived RNA.

RNA has been extracted and analysed from in vivo-derived Mycobacterium avium subspecies paratuberculosis recovered from the natural host. The bacteria were selectively extracted from the intestinal tissue of two goats exhibiting clinical signs of Johne's disease. Small intestine was rapidly removed, luminal contents washed away and the mucosa and submucosa harvested. Mycobacteria in this material were released from the macrophages by isotonic lysis and differential centrifugation. RNA was extracted and compared with RNA extracted from bacteria grown in vitro. Real-time polymerase chain reaction was used to analyse the katG gene from the bacterial messenger RNA. The katG mRNA encoding the putative catalase/peroxidase showed differential expression in the in vivo and in vitro-derived samples. We hypothesize that the increase in katG expression for in vivo-derived M. paratuberculosis may represent a response to the oxidative stress encountered within the intra-macrophage environment.

Adaptation, Physiological↗
PubMed2004

The knockout mouse project.

Mouse knockout technology provides a powerful means of elucidating gene function in vivo, and a publicly available genome-wide collection of mouse knockouts would be significantly enabling for biomedical discovery. To date, published knockouts exist for only about 10% of mouse genes. Furthermore, many of these are limited in utility because they have not been made or phenotyped in standardized ways, and many are not freely available to researchers. It is time to harness new technologies and efficiencies of production to mount a high-throughput international effort to produce and phenotype knockouts for all mouse genes, and place these resources into the public domain.

Alleles↗
PubMed2004

Determining the critical micelle concentration of a novel lipid-lowering agent, disodium ascorbyl phytostanyl phosphate (FM-VP4), using a fluorescence depolarization procedure.

The objective of this study was to determine the critical micelle concentration (CMC) of a novel water-soluble plant sterol derivative (FM-VP4) using a fluorescence depolarization method. The CMC was determined by 1,6-diphenyl-1,3,5-hexatriene (DPH) fluorescence depolarization. Test solutions of various concentrations of sodium dodecylsulphate (SDS) as a positive control or FM-VP4 in water were spiked with 2 microL of 4 mM DPH in tetrahydrofuran (THF) and left overnight to equilibrate in a dark chamber. Fluorescence of each solution was measured at room temperature using a Perseptive Biosystems Cytofluor Series 4000 multi-well plate reader. Fluorescence intensity increases as DPH is incorporated into the hydrophobic core of micelles. Thus, the CMC is the value at which an abrupt increase in intensity is observed. These points were observed at 8 mM and 0.014 mM for SDS and FM-VP4, respectively. Sodium dodecylsulphate was used as a positive control and supports the validity of our results, as the literature values of SDS are reported to be between 8-8.3 mM. The CMC of FM-VP4 is reported to be 0.014 mM.

Chemistry, Pharmaceutical↗
PubMed2004

Topotecan in the first-line treatment of small cell lung cancer.

Small cell lung cancer (SCLC) is generally sensitive to first-line chemotherapy, but limited disease often recurs and extensive disease is rarely curable. The most common first-line therapy regimen is cisplatin (Platinol; Bristol-Myers Squibb; Princeton, NJ) plus etoposide (Etopophos; Bristol-Myers Squibb)--PE, which is associated with overall response rates >80% in patients with limited SCLC. Although it is associated with median survival times of approximately 18-20 months for limited disease, PE yields median survival times of only approximately 8-12 months in patients with extensive disease, and symptom palliation becomes the primary therapeutic goal. The toxicities of PE may undermine quality of life and leave patients more susceptible to adverse events during subsequent therapies. Topotecan (HYCAMTIN; GlaxoSmithKline; Philadelphia, PA), an established treatment for recurrent SCLC, is being investigated in the first-line setting because of its novel mechanism of action; predictable, noncumulative, and manageable toxicities; and potential synergy with other active agents. Several recent phase II trials have generated promising results for topotecan-based combination regimens, including topotecan/paclitaxel (TAXOL; Bristol-Myers Squibb) (overall response rates 45%-100%), topotecan/etoposide (overall response, 95%), and topotecan, paclitaxel, and platinum agent triplets (overall response rates 51%-93%). The most frequent serious toxicity associated with these regimens was reversible and noncumulative neutropenia, which was generally manageable with supportive care. Additional clinical trials to investigate topotecan-based combination regimens and confirm their role in the first-line treatment of SCLC are under way.

Antineoplastic Agents↗
PubMed2004

Update on the role of topotecan in the treatment of non-small cell lung cancer.

Non-small cell lung cancer (NSCLC) is an aggressive disease that is generally resistant to chemotherapy. As a result, the prognosis for patients with NSCLC is poor. Currently, platinum-based regimens are the standard of care for patients with advanced NSCLC. However, these regimens are associated with severe and often cumulative hematologic and nonhematologic toxicities, limiting dose intensity. Therefore, novel chemotherapeutic agents and combination regimens may improve the outcome for these patients. A variety of new agents and combinations have been investigated in the treatment of NSCLC. However, to date, no clearly superior single-agent or combination regimen has emerged. Topotecan (Hycamtin; GlaxoSmithKline; Philadelphia, PA), a topoisomerase I inhibitor, is currently approved for the treatment of patients with relapsed small cell lung cancer (SCLC) and is associated with manageable, noncumulative, hematologic toxicities. In addition, topotecan demonstrates a favorable nonhematologic tolerability profile compared with agents currently used in the treatment of patients with NSCLC. The success of topotecan in patients with SCLC has made it an attractive option in the NSCLC setting. Topotecan-based combination regimens in the first-line treatment of NSCLC have demonstrated promising antitumor activities with favorable toxicity profiles. Many topotecan combination regimens have induced stable disease, a response that may offer meaningful clinical benefit in the palliative treatment of patients with advanced disease. Topotecan plus gemcitabine (Gemzar; Eli Lilly and Company; Indianapolis, IN) and single-agent topotecan may be particularly appropriate for patients in the second-line setting, in which palliation of symptoms is an important outcome of chemotherapy. Herein, the future role of topotecan in the first- and second-line treatment of NSCLC and the potential role of resistance mechanisms obtained from in vivo dose-response studies in designing future combination regimens are discussed.

Antineoplastic Agents↗
PubMed2002

House dust mite allergens induce proinflammatory cytokines from respiratory epithelial cells: the cysteine protease allergen, Der p 1, activates protease-activated receptor (PAR)-2 and inactivates PAR-1.

In previous studies, we demonstrated that allergenic house dust mite proteases are potent inducers of proinflammatory cytokines from the respiratory epithelium, although the precise mechanisms involved were unclear. In this study, we investigated whether this was achieved through activation of protease-activated receptor (PAR)-1 or -2. Pretreatment of A549 respiratory epithelial cells with the clinically important cysteine protease allergen, Der p 1, ablated subsequent PAR-1, but not PAR-2 agonist peptide-induced IL-6 and IL-8 release. HeLa cells transfected with the plasmid coding for PAR-2, in contrast to PAR-1, released significant concentration of IL-6 after exposure to Der p 1. Exposure of HeLa cells transfected with either PAR-1/enhanced yellow fusion protein or PAR-2/enhanced yellow fusion protein to Der p 1 caused receptor internalization in the latter cells only, as judged by confocal microscopy with re-expression of the receptor within 120-min postenzyme exposure. Der p 1-induced cytokine release from both A549 and transfected HeLa cells was accompanied by changes in intracellular Ca(2+) concentrations. Desensitization studies showed that Der p 1 pretreatment of the A549 cells resulted in the abolition of both trypsin- and PAR-2 agonist peptide-induced Ca(2+) release, but not that induced by subsequent exposure to either thrombin or PAR-1 agonist peptide. These data indicate for the first time that the house dust mite allergen Der p 1-induced cytokine release from respiratory epithelial cells is, in part, mediated by activation of PAR-2, but not PAR-1.

Allergens↗
PubMed2002

An HPLC method for the measurement of 5-fluorouracil in human plasma with a low detection limit and a high extraction yield.

High performance liquid chromatographic (HPLC) techniques for the quantification of 5-fluorouracil (5-FU) in human plasma have been reported in the literature, however, a low limit of detection was generally found to result in a comparatively low extraction yield. We have developed a simple, rapid and sensitive HPLC method for the measurement of 5-FU in plasma which provides both a low limit of quantification and a high extraction yield. This method involves the solid phase extraction of 5-FU from a 500 microl plasma sample. The extract is then injected into an HPLC system equipped with a C18 (mu)Bondapak column, and a UV detector set at 260 nm. Ethyl acetate and potassium dihydrogen phosphate are used for the solid phase extraction and the HPLC mobile phase, respectively. This method provides in a good baseline, a sharp and symmetrical peak for 5-FU, and a high resolution between 5-FU and the internal standard. The retention time of 5-FU using this method is 4.7 min with a limit of detection of 5 ng/ml, and an extraction yield of 96.2+/-0.5% (SE). The next injection is possible in 11 min, and the coefficients of variation are 4.2-8.9% for interday precision, and 5.2-10.6% for day-to-day reproducibility. An HPLC method has been developed that has a low limit of detection and a high extraction yield. This technique was successfully applied in a clinical pharmacokinetic study of 5-FU.

Chromatography, High Pressure Liquid↗