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Biomedical subjects

C McKenna

Publications and source records attributed to C McKenna.

At least 19 recordsLinked to original sources
PubMed2006

Opacity measurements of a hot iron plasma using an x-ray laser.

The temporal evolution of the opacity of an iron plasma at high temperature (30-350 eV) and high density (0.001-0.2 g cm-3) has been measured using a nickel-like silver x-ray laser at 13.9 nm. The hot dense iron plasma was created in a thin (50 nm) iron layer buried 80 nm below the surface in a plastic target that was heated using a separate 80 ps pulse of 6-9 J, focused to a 100 microm diameter spot. The experimental opacities are compared with opacities evaluated from plasma conditions predicted using a fluid and atomic physics code.

Journal Article↗
PubMed2000

Paroxysmal kinesigenic dyskinesia and infantile convulsions: clinical and linkage studies.

OBJECTIVE: To clinically characterize affected individuals in families with paroxysmal kinesigenic dyskinesia (PKD), examine the association with infantile convulsions, and confirm linkage to a pericentromeric chromosome 16 locus. BACKGROUND: PKD is characterized by frequent, recurrent attacks of involuntary movement or posturing in response to sudden movement, stress, or excitement. Recently, an autosomal dominant PKD locus on chromosome 16 was identified. METHODS: The authors studied 11 previously unreported families of diverse ethnic background with PKD with or without infantile convulsions and performed linkage analysis with markers spanning the chromosome 16 locus. Detailed clinical questionnaires and interviews were conducted with affected and unaffected family members. RESULTS: Clinical characterization and sampling of 95 individuals in 11 families revealed 44 individuals with paroxysmal dyskinesia, infantile convulsions, or both. Infantile convulsions were surprisingly common, occurring in 9 of 11 families. In only two individuals did generalized seizures occur in later childhood or adulthood. The authors defined a 26-cM region using linkage data in 11 families (maximum lod score 6.63 at theta = 0). Affected individuals in one family showed no evidence for a shared haplotype in this region, implying locus heterogeneity. CONCLUSIONS: Identification and characterization of the PKD/infantile convulsions gene will provide new insight into the pathophysiology of this disorder, which spans the phenotypic spectrum between epilepsy and movement disorder.

Adolescent↗
PubMed2000

Effect of short-term aspirin use on C-reactive protein.

Markers of inflammation, such as C-reactive protein (CRP) and fibrinogen, have been shown to be predictive of cardiovascular disease. In the Physicians Health Study, the magnitude of reduction in the risk of myocardial infarction with aspirin therapy was related to baseline CRP levels, raising the possibility that the protective effect of aspirin may be due to antiinflammatory properties in addition to its antiplatelet effect. We therefore investigated whether aspirin therapy lowers CRP levels. Because heavy physical exertion is a well-known trigger of myocardial infarction, we also investigated the effect of aspirin on CRP levels before and after strenuous exercise. Thirty-two healthy men, aged 29 +/- 6 years, were enrolled in a randomized, double-blind, parallel study. Blood samples were obtained immediately before and after maximal treadmill exercise at baseline and following 7 days of aspirin therapy (81 or 325 mg). The levels of CRP, as measured by ELISA, increased by 13% following exercise (P < 0.0001). However, aspirin did not significantly alter CRP levels, either at rest (0.81 +/- 0.13 mg/L before aspirin vs. 0.78 +/- 0.13 mg/L on aspirin) or following exercise (0.92 +/- 0.13 mg/L before aspirin vs. 0.86 +/- 0. 13 mg/L on aspirin), P = 0.73. When the resting and postexercise data were combined, the levels were 0.87 +/- 0.13 mg/L before aspirin and 0.82 +/- 0.13 mg/L on aspirin (a nonsignificant 6% reduction, P = 0.20). In conclusion, in healthy male subjects CRP levels were not significantly reduced by short-term aspirin therapy. Our data, taking together with other reports, suggest that aspirin may not affect the levels of inflammatory markers. However, further studies are needed with a longer duration of therapy, among subjects with coronary heart disease, and using additional markers of inflammation besides CRP to determine the long-term effects of aspirin use.

Acute-Phase Proteins↗
PubMed2000

Couples' shared participation in novel and arousing activities and experienced relationship quality.

Using a newspaper questionnaire, a door-to-door survey, and 3 laboratory experiments, the authors examined a proposed effect of shared participation in novel and arousing activities on experienced relationship quality. The questionnaire and survey studies found predicted correlations of reported shared "exciting" activities and relationship satisfaction plus their predicted mediation by relationship boredom. In all 3 experiments, the authors found predicted greater increases in experienced relationship quality from before to after participating together in a 7-min novel and arousing (vs. a more mundane) task. Comparison with a no-activity control showed the effect was due to the novel-arousing task. The same effect was found on ratings of videotaped discussions before and after the experimental task. Finally, all results remained after controlling for relationship social desirability. Results bear on general issues of boredom and excitement in relationships and the role of such processes in understanding the typical early decline of relationship quality after the honeymoon period.

Adolescent↗
PubMed1999

Upright posture and maximal exercise increase platelet aggregability and prostacyclin production in healthy male subjects.

BACKGROUND: It is well accepted that heavy physical exertion can trigger the onset of myocardial infarction, but the mechanism is uncertain. As platelet and endothelial function play an important role in thrombotic events, platelet and prostacyclin responses to maximal treadmill exercise were studied. METHODS/RESULTS: The study subjects were 40 healthy men, mean (SEM) age 29 (5) years. Platelet aggregation was measured on a four channel aggregometer. Plasma 6-keto-prostaglandin F1alpha was analysed using an enzyme immunoassay technique. Upright posture and exercise produced an increase in platelet aggregability, as indicated by a fall in the threshold concentration of adrenaline (epinephrine) from 7.6 (1.5) microM at rest to 4.3 (1.0) microM after exercise (p = 0.002). The collagen lag time became significantly shorter with exercise (from 79.1 (3.1) seconds at rest to 71.9 (2.6) seconds after exercise, p = 0.003). Exercise was also associated with a 55% increase in plasma 6-keto-prostaglandin F1alpha (from 38.1 (75%CI 29.0 to 46.5) pg/ml at rest to 59.2 (47.3 to 66.8) pg/ml after exercise, p<0.001). CONCLUSIONS: In healthy male subjects, upright posture and maximal exercise increased platelet aggregability but this increase was counteracted by an increase in prostacyclin production. In patients with endothelial dysfunction, a reduced prostacyclin response to exercise may promote a transient prothrombotic imbalance that may trigger cardiovascular disease onset.

Adult↗
PubMed1998

Enhanced coronary vasa vasorum neovascularization in experimental hypercholesterolemia.

Coronary arteries contain a network of vasa vasorum in the adventitia. The three-dimensional anatomy of the vasa vasorum in early coronary atherosclerosis is unknown. This study was designed to visualize and quantitate the three-dimensional spatial pattern of vasa vasorum in normal and experimental hypercholesterolemic porcine coronary arteries, using a novel computed tomography technique. Animals were killed after being fed either a high cholesterol diet (n = 4) or a control diet (n = 4) for 12 wk. The proximal left anterior descending coronary artery was removed from the heart, scanned, and reconstructed, and quantitation of vasa vasorum density was performed. Two different types of vasa vasorum were defined: first-order vasa vasorum ran longitudinally parallel to the vessel and second-order originated from first-order vasa circumferentially around the vessel wall. Compared with controls in hypercholesterolemic coronary arteries, there was a significant increase in the area of the vessel wall (3.86+/-0.22 vs. 8.07+/-0.45 mm2, respectively, P < 0.01) and in the density of vasa vasorum (1. 84+/-0.05/mm2 vs. 4.73+/-0.24/mm2; respectively, P = 0.0001). This occurred especially by an increase of second-order vasa vasorum and disorientation of normal vasa vasorum spatial pattern. This study suggests that adventitial neovascularization of vasa vasorum occurs in experimental hypercholesterolemic coronary arteries and may be a part of the early atherosclerotic remodeling process.

Animals↗
PubMed1998

Adventitial vasa vasorum in balloon-injured coronary arteries: visualization and quantitation by a microscopic three-dimensional computed tomography technique.

OBJECTIVES: The objective of this study was to examine the quantitative response of the adventitial vasa vasorum to balloon-induced coronary injury. BACKGROUND: Recent attention has focused on the role of vasa vasorum in atherosclerotic and restenotic coronary artery disease. However, the three-dimensional anatomy of these complex vessels is largely unknown, especially after angioplasty injury. The purpose of this study was to visualize and quantitate three-dimensional spatial patterns of vasa vasorum in normal and balloon injured porcine coronary arteries. We also studied the spatial growth of vasa vasorum in regions of neointimal formation. A novel imaging technique, microscopic computed tomography, was used for these studies. METHODS: Four pigs were killed 28 d after coronary balloon injury, and four pigs with uninjured coronary arteries served as normal controls. The coronary arteries were injected with a low-viscosity, radiopaque liquid polymer compound. Normal and injured coronary segments were scanned using a microscopic computed tomography technique. Three-dimensional reconstructed maximum intensity projection and voxel gradient shading images were displayed at different angles and voxel threshold values, using image analysis software. For quantitation, seven to 10 cross-sectional images (40 normal and 32 balloon injured cross-sections) were captured from each specimen at a voxel size of 21 microm. RESULTS: Normal vasa vasorum originated from the coronary artery lumen, principally at large branch points. Two different types of vasa were found and classified as first-order or second-order according to location and direction. In balloon-injured coronary arteries, adventitial vasa vasorum density was increased (3.16+/-0.17/mm2 vs. 1.90+/-0.06/mm2, p = 0.0001; respectively), suggesting neovascularization by 28 d after vessel injury. Also, in these injured arteries, the vasa spatial distribution was disrupted compared with normal vessels, with proportionally more second-order vasa vasorum. The diameters of first-order and second-order vasa were smaller in normal compared with balloon-treated coronary arteries (p = 0.012 first-order; p < 0.001, second-order; respectively). The density of newly formed vasa vasorum was proportional to vessel stenosis (r = 0.81, p = 0.0001). Although the total number of vasa was increased after injury, the total vascular area comprised of vasa was significantly reduced in injured vessels compared with normals (3.83+/-0.20% to 5.42+/-0.56%, p = 0.0185). CONCLUSIONS: Adventitial neovascularization occurs after balloon injury. The number of new vessels is proportional to vessel stenosis. These findings may hold substantial implications for the therapy of vascular disease and restenosis.

Angioplasty, Balloon, Coronary↗
PubMed1998

Health professionals' responses to multiple sclerosis and motor neurone disease.

This study compares the responses of health professionals to multiple sclerosis (MS) and motor neurone disease (MND) in order to determine similarities and variations in responses to the two disorders and the issues critical to caring for patients with these conditions. Health professionals were more negative about MND compared with MS in terms of the amount they felt able to offer patients, their confidence in managing patients and their ability to convey hope. For a number of issues concerning the management of patients, the level of difficulty experienced by health professionals was similar for both MS and MND. These were resource issues, the health professionals' ability to remain positive in the face of progressive disability, interdisciplinary team problems and difficulties regarding patient care. The main concern of health professionals, for both conditions, was the effect of progressive disability on the patient. For MND, management issues which health professionals found comparatively more difficult than for MS were patients' short prognosis and impending death, communication problems and progressive disability. Issues which were comparatively more difficult for MS than MND were changes in patients' affect, cognition and personality, problems with planning care because of the disorder's unpredictable course, problems with diagnosis such as making and disclosing the diagnosis, and the tendency for patients to be difficult or demanding. Some notable differences in responses between health professionals in different health care settings were found. The findings have implications for changing health professionals' conceptualization of 'hope', developing ways of improving communication between health professionals in different health care settings so as to enable them to learn from each other's expertise and experiences and redressing gaps in service provision, especially for young people with MS.

Attitude of Health Personnel↗
PubMed1997

Effect of aspirin dosage and enteric coating on platelet reactivity.

Although aspirin is effective in the prevention and treatment of cardiovascular diseases, the optimal dose remains uncertain. The purpose of this study was to compare the platelet inhibitory and prostacyclin-sparing effects of 2 doses (81 and 325 mg) and forms (enteric-coated and regular) of aspirin. Since platelet reactivity has been reported to increase after strenuous exercise, a known trigger of myocardial infarction, subjects were studied following maximal treadmill exercise as well as at rest. Forty male healthy subjects were evaluated using a randomized, double-blind, parallel study design. Blood samples were obtained before and after maximal treadmill exercise at baseline and after 7 days on aspirin therapy. Both enteric and regular aspirin in 81- and 325-mg dosages markedly inhibited adenosine diphosphate and epinephrine-induced aggregation at rest and after exercise. Aspirin also inhibited the platelet response to collagen as assessed by a longer lag time to aggregation. The prolongation of lag time was greater for 325 mg than for 81 mg (100 +/- 7 vs 91 +/- 7; p = 0.04, after exercise). There were no significant dose-related differences in plasma 6-keto-prostaglandin F1alpha level; however, enteric-coated aspirin inhibited the exercise-induced increase in 6-keto-prostaglandin F1alpha to a lesser extent than regular aspirin. Although both doses (81 and 325 mg) and types (regular and enteric-coated) of aspirin inhibited adenosine diphosphate and epinephrine-induced aggregation equally, the 325-mg dose inhibited collagen-induced aggregation to a greater extent than 81 mg. The greater platelet inhibition observed with 325 mg may be clinically relevant in acute coronary syndromes characterized by plaque rupture with extensive collagen exposure and platelet activation.

6-Ketoprostaglandin F1 alpha↗
PubMed1997

Systemic allergic reaction following ingestion of undeclared peanut flour in a peanut-sensitive woman.

BACKGROUND: Although peanuts and peanut butter are well recognized as food allergens, few reports describe allergic reactions associated with eating peanut flour. OBJECTIVE: To describe an allergic reaction that occurred in a peanut-sensitive woman who ate undeclared peanut flour that was part of a flavor ingredient contained in a dry soup mixture, and to estimate the amount of peanut protein the patient ingested. METHODS: The patient was interviewed, medical records from her emergency room visit were reviewed, and the manufacturer of the soup mix was investigated to ascertain the proportion of the soup mix constituted by the undeclared peanut flour. RESULTS: Minutes after ingesting the soup, a 33-year-old woman experienced a systemic allergic reaction. She was treated successfully in the emergency room with intravenous fluids, corticosteroids, and diphenhydramine. Investigation of the soup manufacturer revealed that undeclared peanut flour was a component of a flavoring ingredient in the soup. Based on the concentration of peanut flour in the flavoring, we estimated the patient ate approximately 45 mg of peanut protein. CONCLUSIONS: Inadvertent ingestion of peanut flour by peanut-sensitive individuals may lead to systemic allergic reactions.

Adult↗
PubMed1997

Survival following traumatic rupture of the heart in a child.

Blunt force trauma to the chest can result in rupture of the heart. We report the youngest survivor of this injury, followed by a literature review, description of the epidemiology, and mechanism and guidelines for diagnosis and aggressive management.

Child↗
PubMed1996

Stress-induced hemodynamic and hemostatic changes in patients with systemic hypertension: effect of verapamil.

Stress-induced hemodynamic and hemostatic responses may acutely trigger atherosclerotic plaque disruption and thrombosis leading to myocardial infarction. This study was designed to evaluate the responses to three stressors and to determine if once-daily sustained release verapamil (Verelan) modified these responses. We studied 13 patients with mild to moderate hypertension in a randomized, double-blind, placebo-controlled crossover trial. After 4 weeks of therapy, patients were evaluated following assumption of the upright posture, mental stress, and cold pressor test. During placebo, the stressors produced an increase in systolic pressure (144 +/- 2 to 167 +/- 3 mmHg, p < 0.001), heart rate (70 +/- 2 to 77 +/- 2 beats/ min, p < 0.001), and platelet aggregability to adenosine diphosphate (threshold concentration fell from 2.8 +/- 0.4 to 1.9 +/- 0.1 microM, p = 0.05) and epinephrine (3.4 +/- 0.9 to 1.6 +/- 0.6 microM, p < 0.001). Verapamil lowered systolic pressure at baseline (144 +/- 2 to 134 +/- 2 mmHg, p < 0.001), and after stress (167 +/- 3 to 154 +/- 3 mmHg, p < 0.001), but did not alter the absolute increase with stress. During verapamil, platelet reactivity did not increase with stress, and the post-stress response to epinephrine was reduced (higher threshold concentration) compared with placebo (3.9 +/- 1.3 vs. 1.5 +/- 0.3 microM, p = 0.05). Verapamil also reduced the response to collagen (increased lag time) at baseline and after stress (111 +/- 9 vs. 91 +/- 3 s, p < 0.01). We conclude that verapamil blunted potentially harmful stress-induced hemodynamic and hemostatic changes. Further studies are required to determine whether these effects translate into a lower incidence of acute cardiovascular events.

Adenosine Diphosphate↗
PubMed1995

Molecular cytogenetic analysis of monosomy 7 in pediatric patients with myelodysplastic syndrome.

Monosomy 7 is a non-random cytogenetic abnormality that is frequently associated with myelodysplastic syndromes (MDS). Twenty-four bone marrow samples from five pediatric patients with MDS were analysed using both traditional and interphase cytogenetic analysis. The majority of the metaphases were monosomic for chromosome 7 while interphase cytogenetic analysis consistently detected a disomic cell population in nondividing cell populations. This suggests that the monosomy 7 cells have a distinct proliferative advantage compared to the disomic cell population. The results demonstrate that interphase cytogenetic analysis provides important cytogenetic information about non-dividing cell subpopulations, enhancing our understanding of the cell dynamics of normal and monosomy 7 cells in MDS.

Adolescent↗