Comparison of coronary artery computed tomography versus fluoroscopy for the assessment of coronary artery disease prognosis.
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Age Distribution↗
Biomedical subjects
A J Taylor
Publications and source records attributed to A J Taylor.
Ultrafast conductivity dynamics in colossal magnetoresistance manganites.
Ultrafast picosecond measurements of optically induced changes in the absolute conductivity (0.4-1.0 THz) of La0.7M0.3MnO3 thin films ( M = Ca, Sr) from 10 K to approximately 0.9 Tc reveal a two-component relaxation. A fast, approximately 2 ps, conductivity decrease arises from an optically induced modification of the effective phonon temperature. The slower component, related to spin-lattice relaxation, has a lifetime that increases upon approaching Tc from below in accordance with an increasing spin specific heat. We show that, for T<<Tc, partial differential sigma/ partial differential T is primarily determined by thermally disordered phonons while spin fluctuations dominate near Tc.
Journal Article↗
Ultrafast dynamics of electron thermalization in gold.
Time-resolved surface second-harmonic generation (SHG) is used to probe electron relaxation processes in gold following intense laser excitation at 1.55 eV. For the first time, an electron temperature ( T(e)) dependent enhancement in the SHG signal is clearly observed at T(e) above 0.7 eV, which is shown to relate to the thermalization of nonequilibrium hot electrons. Therefore, the relaxation dynamics of the transient nonequilibrium electrons in the high T(e) regime is directly resolved by monitoring the time evolution of the SHG signal.
Journal Article↗
Defining moments in medicine. Internal medicine.
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History, 20th Century↗
A comparison of four stent designs on arterial injury, cellular proliferation, neointima formation, and arterial dimensions in an experimental porcine model.
The stent-artery interactions of different stent designs have implications for their clinical effects. We studied four different stent designs to compare their effects on arterial injury, cellular proliferation, neointima formation, and arterial dimensions. Eighteen nonatherosclerotic miniswine underwent random placement of 52 coronary stents (3.0 mm), including self-expanding nitinol stents (no postdilation; Radius, n = 13) and balloon-expandable stents (8 atm x 45 sec; Palmaz-Schatz, n = 13; BX, n = 12; and Multilink, n = 14). Cellular proliferation was determined by S-phase labeling with BrdU at 7, 14, and 28 days. Proliferation, injury scores, and arterial morphometry were blindly evaluated. All four stent designs had similar injury scores, cellular proliferation indexes (neointimal and medial), and adventitial areas. Nitinol stents resulted in a twofold increase in neointimal area and thickness in 28-day vessels (P = 0.002). However, lumen area was similar for all stent designs because of an offsetting expansion in vessel area in nitinol stents (20% greater than balloon-expandable stents) occurring between 7 and 14 days after stent deployment (P = 0.03). Reduced neointimal cell density in nitinol stents (20% less than balloon-expandable stents, P = 0.012) suggests that extracellular matrix expansion accounts for the larger neointima in nitinol stents. Self-expansion of nitinol stents within normal porcine arteries results in a similar degree of arterial injury compared to balloon-expandable stent designs. Progressive enlargement of nitinol stents between 7 and 14 days after deployment is associated with the development of a larger, matrix-rich neointima, with a preserved lumen area. Cathet Cardiovasc Intervent 2001;53:420-425. Published 2001 Wiley-Liss, Inc.
Alloys↗
Dietary intakes of selected elements from longitudinal 6-day duplicate diets for pregnant and nonpregnant subjects and elemental concentrations of breast milk and infant formula.
As part of a longitudinal investigation into mobilization of lead from the maternal skeleton during pregnancy and lactation, we have determined the daily intake of selected elements (hereafter called micronutrients) for various subjects and compared these intakes with recommended and/or published intakes, especially those of the United States, through the U.S. National Health and Nutrition Examination Survey (NHANES). We also sought to ascertain whether there was any seasonal effect in the diets. Six-day duplicate diets were collected from 15 pregnant and 16 nonpregnant migrants to Australia, 6 pregnant Australian control subjects, and 8 children of nonpregnant migrants (6 to 11 years). Samples of breast milk and infant formula were also analyzed. Blended samples were analyzed by inductively coupled plasma mass spectrometry for the elements Ca, Cu, Fe, Mg, P, K, Na, Zn, Ba, Sr, and Pb. Daily intakes of micronutrients were only about half of the daily intake estimated for non-Hispanic white females and infants in the U.S. NHANES III. Estimates of daily intakes from breast milk were also considerably lower for the migrant and Australian infants compared with the values extracted from tables of food composition and dietary recall for non-Hispanic white infants in the U.S. NHANES III. For example, Ca was a factor of approximately 3 times lower, Fe approximately 50, and Zn approximately 4. We consider our estimates a reliable indication of the daily intakes for several reasons, including the collection of up to nine quarterly collections of 6-day duplicate diets and retention of subjects in a longitudinal prospective study. The low intakes of the essential elements such as Ca, Fe, and Zn in all these population groups are of potential concern from a public health viewpoint.
Adult↗
Pathophysiology of calcium deposition in coronary arteries.
BACKGROUND AND MORPHOLOGIC STUDIES: Because coronary artery calcification correlates highly with plaque burden, it is an excellent disease marker for atherosclerosis. However, it is not a sensitive indicator of disease activity, and does not predict luminal compromise because of compensatory remodeling. In addition, most data do not support the concept that plaque calcification is related to plaque instability. Plaques demonstrating acute rupture usually show mild or moderate calcification, and biophysical models do not predict that calcium should result in an increased propensity to rupture. This review outlines morphologic studies relating calcification to risk factors and coronary plaque morphology.
Age Factors↗
In vivo measurement of flavour release from mixed phase gels.
Flavour release was investigated from pure gelatin, pure agarose and mixed gelatin-agarose gels, all containing 25% sucrose and flavoured with p-cymene, ethyl butyrate, pyrazine and ethanol. Gels were characterised by optical microscopy, and rheological techniques to determine phase separation, elastic modulus and melting temperature. Volatile release was measured by monitoring the four volatiles in the expired air from one individual eating the gels, using Atmospheric Pressure Chemical Ionisation-Mass Spectrometry. The release pattern of p-cymene was not affected by gel type. The release of ethanol, ethyl butyrate and pyrazine was affected to different extents by the matrix suggesting that both the properties of the volatile and the matrix determine volatile release in vivo.
Flavoring Agents↗
Infusion of volatile flavor compounds into low-density polyethylene.
Supercritical fluids can extract components from some matrixes (e.g., fat and flavors from food) as well as infusing additives into synthetic polymer matrixes. To study the feasibility of infusing flavors into matrixes as a potential flavoring mechanism, a wide range of volatile flavor compounds was infused into a well-defined synthetic polymer (low-density polyethylene) using supercritical carbon dioxide. The polymer was then extracted, and the amount of infused compound was determined. The effects of time, temperature, pressure, rate of depressurization, volatile concentration, and volatile properties on the degree of infusion were studied. Infusion with supercritical carbon dioxide achieved much higher loadings of the polymer (0.01 to 6.87 mg/g LDPE, depending on the volatile molecule being infused) compared to those achieved by static diffusion. Forty-five volatiles were infused, from which a model was developed to predict infusion as a function of certain physicochemical properties.
Chemical Phenomena↗
Volatile release from an emulsion: headspace and in-mouth studies.
The headspace concentrations of three esters above solutions containing emulsified lipids were more resistant to dilution by a stream of gas than those above water alone. The effect was greatest for ethyl octanoate, and least for ethyl butyrate, with ethyl hexanoate showing intermediate behavior. This correlated with their solubility in the lipid fraction of the emulsion. Headspace analysis (comparing the emulsion with water) underestimated the release of the esters during consumption. The ratios observed between water and emulsion systems were different for the maximum breath concentration compared with headspace analysis. The emulsion appears to have acted as a reservoir for volatile release, counteracting the effects of sample dilution by saliva.
Administration, Inhalation↗
Verification of a mouth simulator by in vivo measurements.
The volatile content of the effluent from the retronasal aroma simulator (RAS) was compared with that of human breath using mass spectroscopy (MS-Nose). The ratios of volatile compounds from the RAS were closely related to those from the panelists' breath with the correlation coefficients ranging from 0.97 to 0.99 from model food systems. A greater sensitivity using the RAS was achieved because higher concentrations of volatiles in the MS-Nose were produced from the RAS than from the breath. In analyzing the effects on volatility of RAS parameters including airflow rate, temperature, saliva ratio, and blending speed, airflow rate had the greatest effect. The correlation coefficients for the real food systems studied ranged from 0.83 to 0.99. The RAS gives a good approximation of time-averaged flavor release in the mouth as defined by breath-by-breath measurements.
Adult↗
Effect of salivary components on volatile partitioning from solutions.
Partition of fourteen volatile compounds, representing the diverse physicochemical properties of aroma compounds, was measured by static equilibrium headspace in solutions containing the components of artificial saliva, either singly or in mixtures. Comparison of a bovine salivary mucin and pig gastric mucin showed no significant difference in partition behavior of the volatiles, so gastric mucin was used. Mucin viscosity changed with pH, but binding of volatile compounds did not show a marked dependence on pH. All combinations of the salivary components were tested for their effect on partition. Three types of behavior were noted. Partition of some compounds was unaffected by mucin, and with other compounds mucin decreased partition, whereas another group showed a decrease with mucin that was affected by the presence of salivary salts and sugar. When volatiles or sugar were added to a mucin solution, the final headspace concentration depended on the order of addition, indicating some competition for binding. These solute-mucin effects are discussed in relation to mucin structure and behavior in solution.
Animals↗
Exercise induced leg pain in young athletes misdiagnosed as pain of musculo-skeletal origin.
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Adult↗
C-reactive protein is not associated with the presence or extent of calcified subclinical atherosclerosis.
BACKGROUND: Both high-sensitivity C-reactive protein (hsCRP) and electron beam computed tomography (EBCT) coronary artery calcification (CAC) are valid markers of cardiovascular risk. It is unknown whether hsCRP is a marker of atherosclerotic burden or whether it reflects a process (eg, inflammatory fibrous cap degradation) leading to acute coronary events. METHODS: A nested case-control study was performed of 188 men enrolled in the Prospective Army Coronary Calcium study. The serum hsCRP levels (latex agglutination assay) were evaluated in subjects with CAC (CAC score >0, n = 94) and compared with age- and smoking status-matched control subjects (CAC score 0, n = 94). RESULTS: Levels of hsCRP in the highest quartile were related to the following coronary risk factors: smoking status, low-density lipoprotein cholesterol, body mass index, glycosylated hemoglobin, fibrinogen, and homocysteine. The mean hsCRP level was similar in cases (+CAC, 0.20 +/- 0.22 mg/dL) and controls (-CAC, 0.19 +/- 0.21 mg/dL; P =.81) and was unrelated to the log-transformed CAC score (r < 0.01, P =.91). Multivariable analysis controlling for standard risk factors, aspirin, and statin therapy found only that low-density lipoprotein cholesterol was related to CAC. CONCLUSIONS: Despite associations with standard and emerging cardiovascular risk factors, hsCRP is unrelated to the presence and extent of calcified subclinical atherosclerosis. This implies that CAC (a disease marker) and hsCRP (a process marker) may be complementary for the prediction of cardiovascular risk.
Adult↗
Design and rationale of the ARBITER trial (Arterial Biology for the Investigation of the Treatment Effects of Reducing Cholesterol)--a randomized trial comparing the effects of atorvastatin and pravastatin on carotid artery intima-media thickness.
BACKGROUND: As a class, statins are remarkably effective in reducing low-density lipoprotein (LDL) cholesterol, and several of these drugs have now been shown to reduce coronary heart disease morbidity and mortality. However, several important controversies in the use of statins remain to be answered by clinical trials. For example, it is controversial whether marked cholesterol reduction to levels below 100 mg/dL would further reduce the incidence of coronary heart disease. Furthermore, concerns about differences among statins for nonlipid effects has raised the concern that the assumption of a class effect is premature until head-to-head clinical trials are completed. METHODS: Arterial Biology for the Investigation for the Treatment Effects of Reducing Cholesterol (ARBITER) is a single-center, randomized, active-controlled study comparing the efficacy of high-dose atorvastatin (80 mg/d) and pravastatin (40 mg/d) in patients being treated for either the primary or secondary prevention of coronary heart disease. This trial will enroll up to 200 patients for the primary end point of the mean change in intima-media thickness of the common carotid artery. This effect will be evaluated over a treatment duration of 12 months. Secondary end points include the effects of statin therapy on inflammatory and hemostatic markers (C-reactive protein and fibrinogen). CONCLUSION: ARBITER will provide important data on the role of marked LDL reduction and the "class effect" theory of statin therapy in cardiovascular medicine.
Atorvastatin↗
Do conventional risk factors predict subclinical coronary artery disease? Results from the Prospective Army Coronary Calcium Project.
BACKGROUND: Recent guidelines recommend against the routine use of coronary artery calcification (CAC) detection because the additive value over clinical prediction tools is uncertain. We compared CAC, with use of electron-beam computed tomography (EBCT), with clinical and serologic coronary risk factors for the identification of patients with increased coronary heart disease risk. METHODS AND RESULTS: We studied 630 active-duty US Army personnel (39-45 years old) without known coronary artery disease (CAD) who were undergoing a routine physical examination as required by regulations. Each participant underwent clinical and serologic risk factor screening and EBCT. The cohort (mean age 42 +/- 2 years, 82% male) had a low predicted risk of coronary events (mean 5-year Framingham risk index [FRI] 1.6% +/- 1.2%). The prevalence of coronary calcification was 17.6% (male 20.6%, female 4.3%). Significant univariate correlates of CAC were total and low-density lipoprotein [LDL] cholesterol, triglycerides, systolic blood pressure, and body mass index. However, only LDL cholesterol was independently associated with CAC. There was a significant but weak relationship between CAC and the Framingham risk index (FRI) (receiver-operator characteristic [ROC] curve area 0.62 +/- 0.03, P <.001), which was not different from the relationship between CAC and LDL cholesterol alone (ROC curve area 0.61 +/- 0.03, P <.001). The prevalence of any CAC in men increased slightly across increasing quartiles of FRI: 17.0%, 20.8%, 33.0%, and 29.2% (P =.033). Other risk factors (family history, homocysteine, insulin, lipoprotein[a], and fibrinogen) were not related to CAC. CONCLUSIONS: In this age-homogeneous, low-risk screening cohort, conventional coronary risk factors significantly underestimated the presence of premature, subclinical calcified coronary atherosclerosis. These data support the potential of CAC detection as an anatomic, plaque-burden diagnostic test to identify patients who may require more intensive risk-reduction therapies, independent of predicted clinical risk.
Adult↗
Seat belt use before and after motor vehicle trauma.
BACKGROUND: Motor vehicle crashes cause significant morbidity and mortality annually. Seat belt use has partially been associated with a decreased risk of morbidity and mortality among those involved in motor vehicle crashes. Persons injured in motor vehicle crashes and not wearing seat belts have an increased risk of admission to trauma centers for motor vehicle crash-related injury. The purpose of this study was to measure changes in seat belt use after discharge among patients admitted to a Level I trauma center for injuries sustained in motor vehicle crashes. METHODS: Patients admitted to a Level I trauma center for injuries sustained in motor vehicle crashes during 1998 were eligible for participation. A telephone interview was conducted with a random sample of 136 eligible patients regarding patterns of seat belt use before and after their collision. Demographic data and clinical characteristics were also collected. The frequency of seat belt use before and after crash involvement was compared for all patients and stratified by age, gender, race, and Injury Severity Score (ISS). RESULTS: Slightly over half (54%) of patients reported "always" wearing a seat belt before their collision compared with 85% afterward. Younger age groups, male subjects, and whites had the largest increases in the frequency of seat belt use after collision (45%, 37%, and 44% increases, respectively). With respect to injury severity, the largest increase in the frequency of seat belt use was among those with ISS of 15 to 25 (82% increase). Significant concordance between patient- and emergency medical service-reported use of seat belts was observed. Among subjects reported by emergency medical service personnel to have been restrained, nearly 90% reported belt use at the time of the telephone interview. The most frequently cited occasion for failure to use seat belts (30%) was when taking short trips. Other reported reasons were forgetting to fasten belts (29%), discomfort (10%), being in a rush (8%), riding in the back seat (4%), and that seat belts were unnecessary when riding with a good driver (3%). CONCLUSION: Involvement in a motor vehicle crash results in increased seat belt use. Prevention efforts should be directed toward those patients who report infrequent use. Patient "converts" to seat belt use after collisions may be useful in public awareness and prevention campaigns.
Accidents, Traffic↗
Ankle to brachial pressure index in normal subjects and trained cyclists with exercise-induced leg pain.
PURPOSE: This study compared ankle to brachial pressure indices (ABPI) before and after maximal exercise in three groups in order to investigate maximal exercise testing and ABPI as a useful procedure for the differential diagnosis of exercise-induced leg pain (EILP) in athletes. METHODS: ABPI measurements were taken before and after cycle ergometer exercise to volitional exhaustion or reproduction of symptoms in three groups: 1) untrained individuals (N = 10, 3 female, 7 male; age 35 +/- 5 yr (mean +/- SD)); 2) trained cyclists (N = 10, 3 female, 7 male; age, 30 +/- 5 yr); and 3) symptomatic group of trained cyclists, complaining of EILP (N = 12, 2 female, 10 male; age, 35 +/- 9 yr). RESULTS: Resting blood pressure indices were similar in all groups. ABPI were reduced (P < 0.05) in all groups after exercise. No differences between left and right legs were noted in the elite and untrained groups; however, a significant difference (P < 0.05) was noted between the nonsymptomatic (0.79 +/- 0.10) and symptomatic (0.61 +/- 0.20) legs in the subjects with EILP. Despite these group results, only three subjects in the symptomatic group met the published criteria (index of < 0.5) for endofibrosis of the external iliac artery. All positive ABPI tests were subsequently confirmed via arteriogram. CONCLUSION: Maximal exercise testing combined with ABPI measurement is a simple noninvasive procedure that may be useful for the examination of EILP. The results of this study suggest that, in cases with unilateral symptoms, a between-leg ABPI difference of 0.18 (at the first minute of recovery) may be considered as a useful additional diagnostic criterion.
Adult↗