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Biomedical subjects

D J Fitzgerald

Publications and source records attributed to D J Fitzgerald.

At least 73 records · Page 4Linked to original sources
PubMed1997

8-epi PGF2 alpha generation during coronary reperfusion. A potential quantitative marker of oxidant stress in vivo.

BACKGROUND: Myocardial reperfusion is believed to be associated with free radical injury. However, indexes of oxidative stress in vivo have been limited by their poor specificity and sensitivity. Isoprostanes are stable products of arachidonic acid formed in a nonenzymatic, free radical-catalyzed manner. We have developed a sensitive and specific assay for one of these compounds, 8-epi prostaglandin (PG) F2 alpha. METHODS AND RESULTS: To address its utility as an index of oxidative stress during coronary reperfusion, we measured urinary levels by gas chromatography/mass spectrometry in a canine model of coronary thrombolysis, in patients with acute myocardial infarction treated with thrombolytic therapy, and in patients after elective coronary artery bypass surgery. Urinary 8-epi PGF2 alpha was unchanged after circumflex artery occlusion in a canine model of coronary thrombolysis (n = 13; 437.2 +/- 56.4 versus 432.7 +/- 55.2 pmol/mmol creatinine) but increased significantly (P < .05) immediately after reperfusion (553.8 +/- 64.7 pmol/mmol). Urinary levels were increased (P < .001) in patients (n = 12) with acute myocardial infarction given lytic therapy (265.8 +/- 40.8 pmol/mmol) compared with age-matched control subjects (n = 20; 91.5 +/- 11.8 pmol/mmol) and patients with stable coronary disease (n = 20; 95.7 +/- 6.3 pmol/mmol). Preoperative levels rose from 113.2 +/- 11.8 to 248.2 +/- 86.3 pmol/mmol at 30 minutes into revascularization to 332.2 +/- 82.6 pmol/mmol by 15 minutes after global myocardial reperfusion (P < .05) and dropped to 181.2 +/- 50.4 pmol/mmol at 30 minutes and 120.2 +/- 9.9 pmol/mmol at 24 hours after bypass surgery (n = 5). Corresponding changes in spin adduct formation, found with electron paramagnetic resonance, were noted in 2 patients. CONCLUSIONS: These data support the hypothesis that free radical generation occurs during myocardial reperfusion. Measurement of isoprostane production may serve as a noninvasive index of oxidative stress.

Adult↗
PubMed1997

Continued thromboxane A2 formation despite administration of a platelet glycoprotein IIb/IIIa antagonist in patients undergoing coronary angioplasty.

Experimental data suggest that formation of thromboxane A2 may be suppressed during administration of a glycoprotein IIb/IIIa antagonist. We determined the dose of one such compound, fradafiban, required to provide > 80% occupancy of the platelet glycoprotein IIb/IIIa and examined its effects on thromboxane A2 formation in patients undergoing PTCA. The dose response to fradafiban and additional effects of aspirin were explored initially in patients with stable coronary artery disease. Fradafiban induced a dose-dependent inhibition of platelet aggregation that correlated with fibrinogen receptor occupancy and plasma drug concentration. Addition of aspirin 300 mg had no effect on these parameters. At the highest dose, mean fibrinogen receptor occupancy was 89.7 +/- 1.2% (n = 3) at 4 hours and platelet aggregation had decreased by 93.4 +/- 2.7%. Eighteen patients undergoing coronary angioplasty were randomized to receive either aspirin 330 mg or that dose of fradafiban producing > 80% fibrinogen receptor occupancy. Platelet aggregation was suppressed throughout the infusion of fradafiban to a greater extent than with aspirin. However, there was a marked increase in urinary excretion of 11-dehydrothromboxane B2 in patients treated with fradafiban: from 1973 +/- 889 to a peak of 9760 +/- 3509 pg/mg creatinine (P = .0046). Despite this evidence of continued platelet activation in vivo, there were no cases of coronary thrombosis. In conclusion, fradafiban suppresses platelet aggregation and may be a useful alternative to aspirin in the prevention of thrombotic events in patients undergoing PTCA. However, there is continued formation of thromboxane A2, which may continue to exert its effects as a potent vasoconstrictor and vascular smooth muscle mitogen.

Administration, Oral↗
PubMed1997

Interaction of a thrombin inhibitor and a platelet GP IIb/IIIa antagonist in vivo: evidence that thrombin mediates platelet aggregation and subsequent thromboxane A2 formation during coronary thrombolysis.

We examined the effect of a specific thrombin inhibitor, Ro 46-6240, alone and combined with an antagonist of the platelet GP IIb/IIIa, Ro44-9883, on the response to tissue-type plasminogen activator in a canine model of thrombolysis. Platelet activity was determined by measuring the excretion of 2,3-dinorthromboxane (TX)B2, an enzymatic metabolite of TXA2. Ro 46-6240 administered before tissue-type plasminogen activator induced a dose-dependent prolongation of the activated partial thromboplastin time and prothrombin time. The time to reperfusion decreased dose-dependently (P < .01) to 10 +/- 6 min vs. 52 +/- 5 min in controls. Ro 46-6240 also prevented reocclusion, which occurred in every case in control experiments. Urinary excretion of 2,3-dinor-TXB2 increased from 3 +/- 1 to 37 +/- 9 ng/mg creatinine in controls after reperfusion. This increase was reduced in a dose-dependent fashion by Ro 46-6240, such that at the highest dose, urinary 2,3-dinor-TXB2 after reperfusion was 5.6 +/- 1 ng/mg creatinine. Similar functional and biochemical effects were seen when a subthreshold dose of Ro 46-6240 was combined with Ro 44-9883. At the dose used, Ro 44-9883 alone abolished platelet aggregation ex vivo but failed to modify the response to tissue-type plasminogen activator or the excretion of 2,3-dinor-TXB2 after reperfusion (51 +/- 6 ng/mg creatinine, n = 3). However, the combination of Ro 44-9883 and Ro 46-6240 reduced the time to reperfusion (40 +/- 8 vs. 68 +/- 15 min; n = 7, P < .05), prevented reocclusion and abolished the rise in urinary 2,3-dinor-TXB2 (5 +/- 1 ng/mg creatinine, n = 4). These findings suggest that thrombin mediates platelet activation during coronary thrombolysis. The increased platelet activity results in platelet aggregation and a subsequent increase in TXA2 formation.

Acetates↗
PubMed1996

Compositional similarities between the human immunodeficiency virus and surface antigens of pathogens.

The genome of the human immunodeficiency virus (HIV) is rich in A but not U and deficient in C but not G. This asymmetric nucleotide bias is the major factor in determining the unusual composition of HIV proteins. In this report, we have identified the cellular genes in the GenBank database that are compositionally similar to HIV in order to further understand the significance of the nucleotide bias of the viral genome. A total of 101 genes in the bacterial and invertebrate subdivisions of the database were found to have a base composition that is similar to the composition of the HIV genome. The identified cellular sequences represent a discrete subset of the database since 81 of the 101 entries code for antigens from pathogens and nearly all of these organisms infect humans. The amino acid compositions of these surface antigens are also similar to the unusual composition of HIV proteins, which are deficient in proline and rich in lysine and other polar residues encoded by A-rich codons. The similarities between the HIV proteins and the immunodominant antigens from other pathogens may indicate a common pathogenic strategy for the promotion of immune dysregulation.

Animals↗
PubMed1996

Furin regulates both the activation of Pseudomonas exotoxin A and the Quantity of the toxin receptor expressed on target cells.

Pseudomonas exotoxin A (PE) binds and enters mammalian cells via the alpha 2-macroglobulin receptor/low density lipoprotein receptor-related protein (LRP). The toxin then requires proteolytic cleavage to generate an enzymatically active fragment with translocates to the cell cytosol and inhibits protein synthesis. To assess the role of furin in determining toxin susceptibility, CHO cells were transfected with a mouse furin gene (CHO+fur cells) and maintained under neomycin selection. Cells expressing the transfected gene were about two- to threefold more sensitive to PE than were cells expressing only a neomycin resistance gene (CHO+neo cells). Possible reasons for the increased toxin sensitivity include the cleavage of a greater number of PE molecules and/or the conversion of more single-chain LRP to the processed, two-chain form. Processing of LRP appears to be necessary to allow the surface display of this receptor. Results of ligand binding studies indicated that the CHO+fur cells displayed about twofold more surface-expressed LRP than did CHO+neo cells. In addition, the in vitro cleavage of PE by recombinant furin enhanced toxin potency about threefold for CHO+neo cells but enhanced it very little for CHO+fur cells. This suggested that CHO+fur cells were processing PE at close to the maximum usable rate. Together these findings suggest that furin is involved in at least two separate protein processing pathways that each contribute to the sensitivity of cells to PE.

ADP Ribose Transferases↗
PubMed1996

Eosinophilic pleural effusion: is it always nondiagnostic?

The presence of eosinophils in the pleural effusion is generally considered nondiagnostic. It usually indicates that the patient has had a previous thoracentesis and that air or blood has come in contact with the effusion. Idiopathic acute eosinophilic pneumonia is characterized by acute onset of pulmonary symptoms with hypoxemia, pulmonary infiltrates, eosinophils in bronchoalveolar lavage fluid, and prompt response to steroid therapy. We report a patient who presented with symptoms of acute pneumonia in which the presence of increased eosinophils in the pleural effusion indicated eosinophilic pneumonia.

Adult↗
PubMed1996

Transdermal modification of platelet function: an aspirin patch system results in marked suppression of platelet cyclooxygenase.

Aspirin inhibits platelet cyclooxygenase and prevents thromboxane A2 (TXA2) production. Although it is an effective antithrombotic, even at a low doses aspirin may induce gastrointestinal toxicity. We examined the feasibility of delivering aspirin transdermally using two patch systems, one without (type A) and one with (type B) the permeation enhancer limonene. Daily application of two type A patches that had a total surface area of 100 cm2 and contained 84 mg/patch resulted in 85% +/- 6% reduction in serum TXB2 in six male subjects by day 14. Suppression of serum TXB2 was less marked in females (32% +/- 16%). Analysis of the residual drug in the patch showed that each patch delivered 18 +/- 3 mg on day 1 and 17 +/- 4 mg on day 14, with no difference between males and females. Daily application of a single patch B that had a surface area of 50 cm2 and contained 120 mg aspirin resulted in 60% +/- 11% suppression of serum TXB2 by day 14 in nine male subjects and 84% +/- 9% suppression by day 21. Analysis of the applied patches showed that patch B delivered 33 +/- 3 mg of aspirin daily. Plasma aspirin and salicylate were determined by gas chromatography, mass spectrometry. No aspirin was detected, whereas plasma salicylate was 157 +/- 38 ng/ml and 133 +/- 20 ng/ml by day 14 with patch A and patch B, respectively. Analysis of aspirin applied by patch to the skin in three subjects showed marked hydrolysis to the inactive product, salicylic acid. Aspirin can be delivered transdermally by patch in a dose that suppresses platelet cyclooxygenase. The delivery rate is low reflecting hydrolysis of the drug in the skin. Delivery is improved by the permeation enhancer limonene. This novel route of delivery may be applicable to other antithrombotics and may limit the risk of gastrointestinal toxicity.

Administration, Cutaneous↗
PubMed1996

Office evaluation of pulmonary function: beyond the numbers.

Pulmonary function testing is useful in evaluating dyspnea, wheezing and cough, determining the severity of pulmonary disease, monitoring the response to therapy and assessing preoperative pulmonary risk. Accurate office spirometry requires routine preventive maintenance, cleaning and calibration of equipment and quality control measures. To obtain a flow-volume loop, the seated or standing patient is instructed to inspire maximally to total lung capacity, exhale as hard, fast and completely as possible (forced vital capacity [FVC]), and inhale quickly and deeply to total lung capacity (TLC). Spirometry reveals both obstructive and restrictive airway disease. Obstruction is characterized by reduced forced expiratory volume in one second (FEV1) and FEV1/forced vital capacity (FEV1/FVC%), and normal to increased TLC and residual volume. Restriction is characterized by reduced TLC and residual volume and normal FEV1/FVC%. Spirometry may also reveal abnormalities of the upper airway, including the nasopharynx, vocal cords, trachea and proximal large airways.

Humans↗
PubMed1995

Circular structures in retroviral and cellular genomes.

A computer program for predicting DNA bending from nucleotide sequence was used to identify circular structures in retroviral and cellular genomes. An 830-base pair circular structure was located in a control region near the center of the genome of the human immunodeficiency virus type I (HIV-I). This unusual structure displayed relatively smooth planar bending throughout its length. The structure is conserved in diverse isolates of HIV-I, HIV-II, and simian immunodeficiency viruses, which implies that it is under selective constraints. A search of all sequences in the GenBank data base was carried out in order to identify similar circular structures in cellular DNA. The results revealed that the structures are associated with a wide range of sequences that undergo recombination, including most known examples of DNA inversion and subtelomeric translocation systems. Circular structures were also associated with replication and transposition systems where DNA looping has been implicated in the generation of large protein-DNA complexes. Experimental evidence for the structures was provided by studies which demonstrated that two sequences detected as circular by computer preferentially formed covalently closed circles during ligation reactions in vitro when compared to nonbent fragments, bent fragments with noncircular shapes, and total genomic DNA. In addition, a single T-->C substitution in one of these sequences rendered it less planar as seen by computer analysis and significantly reduced its rate of ligase-catalyzed cyclization. These results permit us to speculate that intrinsically circular structures facilitate DNA looping during formation of the large protein-DNA complexes that are involved in site- and region-specific recombination and in other genomic processes.

Animals↗
PubMed1995

Cell-type-specific ras mutations but no microsatellite instability in chemically induced mouse skin tumors and transformed 3T3 cells.

In mouse skin, both papillomas/carcinomas or fibrosarcomas can be induced by 7,12-dimethylbenz[alpha]anthracene (DMBA) depending on the mode of administration. Thus, upon DMBA painting (or transplacental exposure by i.p. injection to pregnant mothers) followed by 12-O-tetradecanoylphorbol-13-acetate applications to the skin of CD1 mice, papillomas and carcinomas appeared, whereas fibrosarcomas were induced when DMBA was s.c. injected. Molecular analysis of these tumors revealed that the majority of papillomas (17/20) and carcinomas (9/10) showed DMBA-specific mutations (A to T transversion at the 61st codon) in the Ha-ras gene. On the other hand, many fibrosarcomas (5/9) showed the same mutation only in the Ki-ras gene. When microsatellites were studied in these tumors at nine loci containing CA repeats, none of them showed an instability. In addition, when we analyzed 14 BALB/c 3T3 cell lines transformed by various carcinogens (including 3 clones induced by DMBA which have the A to T mutation in the Ki-ras gene), no changes in CA repeats were observed. These results suggest that DMBA-induced mouse tumors/transformed cells show cell-type-specific ras gene mutations, and these occur independently in the absence of microsatellite instability. While murine cells are considered to be relatively susceptible to cancer induction partially due to genomic instability, our results indicate that microsatellite instability is not induced in these cells by chemical carcinogens.

3T3 Cells↗
PubMed1995

Shed whole blood autotransfusion during aortic aneurysm operation with a modified collection infusion system.

We describe a modified shed whole blood collection and autotransfusion system that allows several options for the processing and autotransfusion of shed blood: use of the Cell Saver (Haemonetics, Braintree, MA) or the ultrafiltration of collected blood, and the autotransfusion of unprocessed shed whole blood. The system has proved useful for transfusion in the setting of thoracic aortic operations, and we describe here our experience in 5 patients undergoing resection of a descending thoracic aortic aneurysm in whom this system was used.

Aged↗
PubMed1995

Creating a dignified option: ethical considerations in the formulation of prehospital DNR protocol.

Increasing numbers of states are recognizing the importance of developing policies to allow Do Not Resuscitate (DNR) orders to be recognized in the prehospital setting, especially by emergency medical personnel. The ethical issues involved in creating such policies have not been widely addressed. Using the experience of developing such a policy for the District of Columbia as a model, we discuss six major ethical issues involved in prehospital DNR order policy development. 1) Can the justification for the policy be grounded in the doctor's duty of beneficence? 2) Should the concept of futility be applied to prehospital DNR orders? 3) How specific should prehospital DNR orders be? 4) How can one maximize patient participation in the prehospital DNR decision? 5) How much consideration ought to be given to the scarcity of health care resources in the development and justification of such policies? 6) Should paramedics be empowered to pronounce DNR patients dead in the field? This discussion ought to be of benefit to all those involved in developing or revising prehospital DNR policies.

Advisory Committees↗