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R S Gibson

Publications and source records attributed to R S Gibson.

At least 145 records · Page 8Linked to original sources

Utility of two-dimensional echocardiography in suspected ascending aortic dissection.

The value of 2-dimensional echocardiography (2-D echo) in patients with suspected ascending aortic dissection was assessed. During a 5.5-year period, 56 consecutive patients underwent bedside 2-D echo for unexplained chest pain possibly due to ascending aortic dissection. Patients with obvious aortic dissection who proceeded directly to aortography were excluded and in all 56 study cases, 2-D echo was the initial diagnostic test. Using standard criteria, 2-D echo correctly identified all 13 patients with ascending aortic dissection. There were 5 false-positive study results and 38 true-negative results, yielding a sensitivity of 100%, specificity of 88% and overall diagnostic accuracy of 91%. In the group of 13 patients with confirmed ascending aortic dissection, 2-D echo identified 4 with pericardial fluid, and 3 of these patients (75%) died within 24 hours. In comparison, 7 patients in the group of 43 without confirmed dissection had pericardial fluid by 2-D echo and only 1 died (p less than 0.001). Finally, in the group of 38 patients with true-negative results, 2-D echo provided useful information in 16 (42%) that assisted or was essential in establishing an alternative diagnosis. However, 5 patients in this group had type III dissection and in none was it identified by 2-D echo. Thus, our data indicate that 2-D echo represents a reliable noninvasive method for rapidly diagnosing ascending aortic dissection at the bedside; offers important prognostic information which is directly related to the presence of pericardial fluid, and provides useful additional information which assists or establishes an alternative diagnosis when ascending aortic dissection is absent.(ABSTRACT TRUNCATED AT 250 WORDS)

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Prognosis with chest pain and normal thallium-201 exercise scintigrams.

The goal of this study was to determine the prognostic value of a normal exercise thallium-201 (TI-201) scintigram by quantitative criteria in a consecutive series of 349 patients with chest pain. Follow-up was obtained in 345 patients (99%) from 8 to 45 months (mean 34 +/- 7). Of these, 60% were men, 26% had typical angina, 21% had chest pain during exercise testing, 29% were unable to achieve 85% or more of maximal predicted heart rate, and in 9% ischemic ST depression (1.0 mm or greater) developed during exercise. At the time of exercise testing, 45% of patients were taking nitrates and 38% were receiving a beta-blocking drug. During the follow-up period, there were 5 cardiac deaths (0.51%/year), of which 2 were sudden, 6 patients had a nonfatal myocardial infarction (MI) (0.61%/year). Two of the 5 patients who died and 1 who had MI had angiographically normal coronary arteries. The event rate was significantly higher (p less than 0.01) in patients referred for early catheterization (5 of 53; 9%) compared with the rate for those not undergoing early angiography (6 of 298; 2%). However, the event rate was similar in those who underwent catheterization with angiographically normal coronary arteries and in those who had significant coronary artery disease.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

A prospective clinical, scintigraphic, angiographic and functional evaluation of patients after inferior myocardial infarction with and without right ventricular dysfunction.

To elucidate the functional and prognostic significance of right ventricular dysfunction after acute inferior wall myocardial infarction, 74 consecutive patients with inferior infarction were prospectively evaluated with gated equilibrium blood pool imaging at rest, submaximal exercise thallium-201 scintigraphy and coronary angiography before hospital discharge. In addition, symptom-limited stress thallium-201 scintigraphy was performed in 61 patients at 3 months, and all patients were followed up clinically for 23 +/- 15 months. Utilizing predetermined radionuclide angiographic criteria, 47 patients (Group I) had normal right ventricular function, 12 patients (Group II) had mild to moderate dysfunction and 15 patients (Group III) had severe right ventricular dysfunction. There were no significant differences among the groups with regard to age, history of prior myocardial infarction, peak creatine kinase values, maximal Killip functional class, number or type of in-hospital complications, left ventricular ejection fraction, prevalence of multivessel disease or the distribution and severity of disease affecting the infarct-related vessel. Exercise tolerance as assessed by treadmill time, blood pressure-heart rate product and peak work load in METS was comparable among the three groups, both before hospital discharge and at 3 month follow-up. No differences in indicators of exercise-induced ischemia were noted among the groups, including the prevalence of redistribution thallium-201 defects, ST segment depression or symptoms of chest pain. Finally, cardiac mortality, reinfarction rate and the incidence of medically refractory angina pectoris were similar in the three groups. Thus, right ventricular dysfunction after acute inferior wall myocardial infarction does not appear to limit exercise tolerance or identify a subgroup of patients at higher risk for recurrent cardiac events.

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The zinc, copper, and selenium status of a selected sample of Canadian elderly women.

The zinc, copper, and selenium status of 90 noninstitutionalized Canadian elderly women (M age = 70.3 years) in a university community and consuming self-selected diets was assessed using hair and serum trace element levels and dietary trace element intakes. Mean (+/- SD) serum zinc and copper levels (analyzed via atomic absorption spectrophotometry, AA) were 1.09 +/- 0.13 and 1.22 +/- 0.29 micrograms/ml, respectively. Mean serum selenium (+/- SD) (analyzed via instrumental neutron activation analysis (INAA) was 0.115 +/- 0.03 micrograms/ml. Median hair trace element values, analyzed via INAA, were 156 for zinc, 12.8 for copper, and 0.63 micrograms/g for selenium. Mean (+/- SD) daily dietary intakes determined via chemical analysis of 1-day diet duplicates were 1.2 +/- .06 mg/d for copper (via AA), 7.6 +/- 3.3 mg/d and 77.6 +/- 44.5 micrograms/d for zinc and selenium (via INAA), respectively, whereas mean copper and zinc intakes (+/- SD) calculated from 3-day records were 1.6 +/- 0.7 and 10.1 +/- 3.5 mg/day, respectively. Median hair and serum trace element values were above the levels associated with deficiencies. Thus the zinc, copper and selenium status of these elderly women appeared adequate.

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Dietary zinc intake and growth during infancy.

Energy, protein, zinc intake, and weight and length were monitored at 3, 6, and 12 months in 50 preterm infants (corrected for gestational age) (mean birthweight, 1,054 +/- 234 g; mean gestation, 29 +/- 2.5 weeks) and 60 full-term infants (mean birthweight, 3,509 +/- 269 g; mean gestation, 40 +/- 1 weeks). Mean energy and protein intake (per kilogram body weight) was higher (p less than 0.05) for the preterm infants at all times and met the recommended levels for preterm infants. No significant differences in zinc intake (per kilogram body weight) between the two groups existed, and at 3 months, mean zinc intake in the preterm group (per kilogram body weight) was below the recommended level for full-term infants. At no time were the growth percentiles of the preterm group equal to those of the full-term group. Multiple regression equations predicting length at 3 months and weight at 12 months for all the infants were significant, the significant variables being length at birth and zinc intake (milligrams per day) at 3 months, and weight at birth and dietary zinc intake (milligrams per day) at 12 months, respectively. Results indicate that zinc intake played a more important role in explaining the length at 3 months and weight at 12 months than did any other variables, including intakes of protein and energy, gestational age, socioeconomic index of the father, midparent height, sex, and age of introduction of solid foods. Results thus support the suggestion that infants, especially those born prematurely, are at risk for inadequate intake of dietary zinc.

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Radionuclide methods of identifying patients who may require coronary artery bypass surgery.

Myocardial thallium-201 (201Tl) scintigraphy or radionuclide angiography performed in conjunction with exercise stress testing can provide clinically useful information regarding the functional significance of underlying coronary artery stenoses in patients with known or suspected coronary artery disease. Knowledge of type, location, and extent of myocardial 201Tl perfusion abnormalities or the severity of exercise-induced global and regional dysfunction has prognostic value. Risk stratification can be undertaken with either radionuclide technique by consideration of the magnitude of the ischemic response and may assist in the selection of patients for coronary artery bypass graft surgery (CABG). In patients with coronary artery disease, delayed 201Tl redistribution observed on exercise or dipyridamole 201Tl scintigraphy, particularly when present in multiple vascular regions and associated with increased lung 201Tl uptake, has been shown to be predictive of an adverse outcome, whereas patients with chest pain and a normal exercise 201Tl scintigram have a good prognosis with medical treatment. Similarly, a marked fall in the radionuclide ejection fraction from rest to exercise has been found to correlate with high-risk anatomic disease. In one published nonrandomized study, patients with coronary artery disease who demonstrated an abnormal ejection fraction response to exercise preoperatively had a better survival with CABG than with medical therapy. Another important application of radionuclide imaging in patients being considered for CABG (particularly those with a depressed resting left ventricular ejection fraction) is the determination of myocardial viability and potential for improved blood flow and enhanced regional function after revascularization. There are certain limitations of exercise 201Tl scintigraphy and radionuclide angiography that can be reduced by improved methods of quantitation of perfusion and function and further development of tomographic imaging approaches.

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Dietary chromium and manganese intakes of a selected sample of Canadian elderly women.

Energy, manganese and chromium intakes of a selected sample of 90 free-living Canadian women (mean age 66.2 +/- 6.2 years) living in a university community and consuming self-selected diets were assessed by chemical analyses of 24-h duplicate diets and via three-day dietary records, collected by the subjects. Mean gross energy intake (determined via bomb calorimetry) was 6.0 +/- 2.4 MJ (1435 +/- 580 kcal) and mean intake of manganese (determined via atomic absorption spectrophotometry) was 3.8 +/- 2.1 mg/day, respectively. Mean and median chromium intakes, analysed via instrumental neutron activation analysis were 96.4 and 77.4 micrograms/day, respectively. The manganese and chromium densities of these diets were higher compared to diets for pre-menopausal women studied earlier, attributed in part to the higher (P less than 0.0003) median intake of tea (360 g) vs 180 g for the pre-menopausal women. No significant differences between the pre and post-menopausal groups in mean intakes (in g) of any other food groups investigated, were found. Silver-plated cutlery may also be a source of adventitious chromium in the diets of these post-menopausal subjects. Nevertheless 22 per cent of the subjects had chromium intakes based on one day duplicate diets, below the US suggested safe limit, which if representative of their habitual chromium intakes, may result in chromium depletion.

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The concentrations of copper, zinc, manganese and selenium in the hair of newborn piglets and their dams.

Instrumental neutron activation analysis was employed to determine the levels of certain trace elements in the hair of newborn piglets and their dams. The mean concentrations (mumoles/mg) of copper, zinc, manganese and selenium in the neonatal piglet hair samples were 222 +/- 55, 4940 +/- 1728, 12.7 +/- 17.1 and 8.9 +/- 5.5, respectively, and in sow hair samples the mean concentrations (mumoles/mg) were 156 +/- 22, 5124 +/- 1927, 31.7 +/- 22.2 and 6.5 +/- 3.7, respectively. The mean copper level was higher (p less than 0.05) in piglet hair compared with sow hair. However the mean concentration of manganese was lower (p less than 0.05) in piglet hair. There was no relationship between the trace mineral levels found in the piglets' hair and the dams' hair. The levels of copper, zinc, manganese and selenium found in piglet hair were shown to be unrelated to the piglet body weight. The feasibility of using porcine hair as a practical biopsy material for trace element analysis is discussed.

Animals↗

Prevalence of high-risk thallium-201 scintigraphic findings in left main coronary artery stenosis: comparison with patients with multiple- and single-vessel coronary artery disease.

To determine the prevalence of high-risk thallium-201 (Tl-201) scintigraphic findings in patients with left main (LM) coronary artery disease (CAD), quantitative exercise Tl-201 scintigrams were analyzed in 295 consecutive patients with angiographic (greater than or equal to 50% stenosis) CAD, of which 43 (14%) had greater than or equal to 50% LM stenosis. A high-risk scintigram was defined as one that demonstrated (1) a LMCAD scintigraphic pattern (greater than or equal to 25% homogeneous decrease in Tl-201 activity in the middle and upper septal and posterolateral walls on the 45 degree left anterior oblique projection); (2) abnormal Tl-201 uptake or washout in multiple vascular scan segments indicative of multivessel disease; and (3) increased lung Tl-201 uptake on the initial anterior projection image. Of the 43 patients with LMCAD, 41 (95%) had an abnormal scintigram. Thirty-three (77%) had 1 or more high-risk scintigraphic findings, including 29 (67%) with a multivessel CAD scan pattern, of which 6 (14%) demonstrated a typical LMCAD pattern; and 18 (42%) with abnormal lung Tl-201 uptake. The prevalence of a high-risk scintigram in patients with LMCAD was significantly greater than that in 53 patients with 3-vessel disease (58%) (p = 0.05), 99 patients with 2-vessel disease (60%) (p = 0.04) and 100 patients with 1-vessel disease (41%) (p less than 0.0001).(ABSTRACT TRUNCATED AT 250 WORDS)

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The interpretation of human hair trace element concentrations.

Scalp hair samples collected from 86 Canadian elderly, non-institutionalized women (mean age 66.6 +/- 6.2 y) on two separate occasions ten weeks apart, were analyzed for Zn, Cu and Mn content. Fasting blood samples were also collected and serum Zn, Cu and albumin content determined. Median hair Zn, Cu and Mn and mean serum Zn and albumin concentrations were not significantly different at the pre- and post-study periods. Furthermore, hair Zn concentrations at the two sampling times were positively and significantly correlated as were hair Cu, hair Mn, serum Zn and serum albumin values. In contrast no significant correlation related the hair and serum Zn values and hair and serum Cu values at any time. The constancy of the hair Zn, Cu and Mn concentrations at the two sampling periods may reflect the homeostatic regulation which controls absorption and hence body trace element content. In addition, results indicate that, after careful laboratory washing, the effects of adventitious contamination on hair trace element content are small, and can be effectively ignored.

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Serum zinc, copper, and selenium concentrations in preterm infants receiving enteral nutrition or parental nutrition supplemented with zinc and copper.

Fifteen enterally fed preterm infants not receiving additional trace element supplements and 22 preterm infants receiving total or partial parenteral nutrition supplemented with zinc at 350 micrograms/kg/day and copper at 20 micrograms/kg/day were examined 1, 7, 14, 21, and 28 days after birth. Mean serum Zn concentrations in the parenteral group remained relatively constant and were significantly higher (P less than 0.01) at day 21 than the value for the enteral group. In contrast, a significant decline in mean serum Zn concentrations occurred between days 1 and 21 in the enteral group. The mean serum Cu concentrations in the parenteral group rose during the first week, and were significantly higher at days 14 and 21 than corresponding values in the enteral group. This trend did not result from copper supplementation alone but was also attributed to the presence of ceruloplasmin in blood transfusions. Mean serum Se concentrations did not change significantly, either between or within the two groups, except during the first week, at which time levels rose in the parenteral group. The addition of Zn, Cu, and probably of Se to parenteral infusates, allows the maintenance of appropriate serum values.

Ceruloplasmin↗

A comparison of the zinc, copper and manganese status of very low birth weight pre-term and full-term infants during the first twelve months.

During a longitudinal study, hair samples and dietary intake data were collected from 50 pre-term (mean birth weight = 1054 +/- 234 g, mean gestational age = 29 +/- 2.5 weeks) and 60 full-term infants (mean birth weight = 3509 +/- 269 g, mean gestational age = 40 +/- 1 weeks) at 3, 6 and 12 months of age. Mean daily zinc, copper and manganese intakes were calculated using three-day dietary records and test-weight data for the breast-fed infants. Hair samples were analyzed for these elements by instrumental neutron activation analyses. The medium hair zinc concentration in the pre-term group at six months (81 micrograms/g) was lower (p less than 0.05) than that of the full-term group (144 micrograms/g) and was associated with lower mean dietary zinc intakes at 3 and 6 months. At 12 months, the median hair copper (12.5 micrograms/g) and manganese (0.18 micrograms/g) concentrations for the pre-term were lower (p less than 0.05) than those of the full-term infants (Cu = 16.5 micrograms/g; Mn = 0.25 micrograms/g) and were also associated with low dietary copper and manganese intakes.

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Relation of therapeutic response to nifedipine to coronary anatomy and motion of S-T segment during unstable angina pectoris.

Of 77 patients hospitalized for unstable angina pectoris and failure of oral, dermal, or intravenous nitrates and/or beta blockade, 81 percent with negligible or single-vessel disease and 55 percent with two- or three-vessel disease showed response (p less than 0.05) to nifedipine therapy. Patients with either S-T elevation or no change during pain responded better (31 of 45) than those with any S-T depression (16 of 32; p less than 0.05). Patients with negligible or single-vessel disease had a higher prevalence of S-T elevation (13 of 16) than patients with two- or three-vessel disease (15 of 31; p = 0.004). S-T motion did not predict response in patients with two- or three-vessel disease, but did predict response in patients with negligible or single-vessel disease. On follow-up study at 9 +/- 8 (range one to 33) months, 39 of 42 who had shown response were free from pain. Three died from infarction without unstable angina. (range one to 33) months, 39 of 42 who had shown response were free from pain. Three died from infarction without unstable angina. Five who showed response had elective bypass surgery. The addition of nifedipine abolished or reduced pain episodes by more than 50 percent in 61 percent of patients with refractory unstable angina pectoris. Patients with negligible or single-vessel disease with S-T elevation benefit most. In patients with two- or three-vessel disease, the type of S-T motion did not predict response. Follow-up of all those with response indicated sustained amelioration by nifedipine therapy. Failure of nifedipine therapy should not be accepted until a dose of 120 mg per day has been achieved, or until intolerable side effects appear.

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Prospective assessment of regional myocardial perfusion before and after coronary revascularization surgery by quantitative thallium-201 scintigraphy.

Because thallium-201 uptake relates directly to the amount of viable myocardium and nutrient blood flow, the potential for exercise scintigraphy to predict response to coronary revascularization surgery was investigated in 47 consecutive patients. All patients underwent thallium-201 scintigraphy and coronary angiography at a mean (+/- standard deviation) of 4.3 +/- 3.1 weeks before and 7.5 +/- 1.6 weeks after surgery. Thallium uptake and washout were computer-quantified and each of six segments was defined as normal, showing total or partial redistribution or a persistent defect. Persistent defects were further classified according to the percent reduction in regional thallium activity; PD25-50 denoted a 25 to 50% constant reduction in relative thallium activity and PD greater than 50 denoted a greater than 50% reduction. Of 82 segments with total redistribution before surgery, 76 (93%) showed normal thallium uptake and washout postoperatively, versus only 16 (73%) of 22 with partial redistribution (probability [p] = 0.01). Preoperative ventriculography revealed that 95% of the segments with total redistribution had preserved wall motion, versus only 74% of those with partial redistribution (p = 0.01). Of 42 persistent defects thought to represent myocardial scar before surgery, 19 (45%) demonstrated normal perfusion postoperatively. Of the persistent defects that showed improved thallium perfusion postoperatively, 75% had normal or hypokinetic wall motion before surgery, versus only 14% of those without improvement (p less than 0.001). Whereas 57% of the persistent defects that showed a 25 to 50% decrease in myocardial activity demonstrated normal thallium uptake and washout postoperatively, only 21% of the persistent defects with a decrease in myocardial activity greater than 50% demonstrated improved perfusion after surgery (p = 0.02). Thus, preoperative quantitative thallium-201 scintigraphy appears useful in predicting response to revascularization surgery, and some persistent defects may revert to normal thallium uptake after surgery. Importantly, the preoperative distinction between viable and nonviable myocardium can be reasonably established by quantitating the amount of persistent reduction in thallium uptake and correlating this with preoperative wall motion.

Coronary Artery Bypass↗

Regional differences in hair zinc concentrations: a possible effect of water hardness.

Hair Zn, Cu, and Mn concentrations were determined by neutron activation procedures in two groups of healthy, Caucasian children aged 4.5 to 5.5 yr from Halifax, Nova Scotia and Guelph, Ontario and consuming soft water (hardness - 33 ppm) and very hard tap water (hardness = 330 ppm), respectively. Median hair Zn level for the Halifax children (26 males and 26 females) was 140 microgram/g, significantly higher (p less than 0.001) than the Guelph children (median = 82 microgram/g; 25 males and 26 females). No significant differences existed between the two groups for median hair Cu and Mn levels (Halifax hair Cu 12.1 microgram/g. Guelph hair Cu 11.0 microgram/g. Halifax hair Mn 0.17 microgram/g. Guelph hair Mn 0.18 microgram/g). The Halifax children were significantly heavier (p less than 0.001) and slightly taller (p = 0.09) than their Guelph counterparts, although mean daily intakes of energy, protein, Zn, Cu, Mn, and dietary fiber, calculated from 3-day food records were not significantly different in the two groups. The large differences in the hair zinc levels may be due to the high concentration of calcium in the Guelph hard water, which may decrease the absorption of zinc.

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Prediction of cardiac events after uncomplicated myocardial infarction: a prospective study comparing predischarge exercise thallium-201 scintigraphy and coronary angiography.

The ability of predischarge quantitative exercise thallium-201 (201T1) scintigraphy to predict future cardiac events was evaluated prospectively in 140 consecutive patients with uncomplicated acute myocardial infarction; the results were compared with those of submaximal exercise treadmill testing and coronary angiography. High risk was assigned if scintigraphy detected 201T1 defects in more than one discrete vascular region, redistribution, or increased lung uptake, if exercise testing caused ST segment depression greater than or equal to 1 mm or angina or if angiography revealed multivessel disease. Low risk was designated if scintigraphy detected a single-region defect, no redistribution, or no increase in lung uptake, if exercise testing caused no ST segment depression or angina, or if angiography revealed single-vessel disease or no disease. By 15 +/- 12 months, 50 patients had experienced a cardiac event; seven died (five suddenly), nine suffered recurrent myocardial infarction, and 34 developed severe class III or IV angina pectoris. Compared with that of patients at low risk, the cumulative probability of a cardiac event was greater in high-risk patients identified by scintigraphy (p less than .001), exercise testing (p = .011), or angiography (p = .007). Scintigraphy predicted low-risk status better than exercise testing (p = .01) or angiography (p = .05). Each predicted mortality with equal accuracy. However, scintigraphy was more sensitive in detecting patients who experienced reinfarction or who developed class III or IV angina. When all 50 patients with events were combined, scintigraphy identified 47 high-risk patients (94%), whereas exercise-induced ST segment depression or angina detected only 28 (56%) (p less than .001). The presence of multivessel disease as assessed by angiography identified nine more patients with events than exercise testing (p = .06). However, the overall sensitivity of angiography was lower than that of scintigraphy (71% vs 94%; p less than .01) because three patients who experienced reinfarction and 10 who developed class III or IV angina had single-vessel disease. Importantly, 12 (92%) of these 13 patients with single-vessel disease who had an event exhibited redistribution on scintigraphy. These results indicate that (1) submaximal exercise 201T1 scintigraphy can distinguish high- and low-risk groups after uncomplicated acute myocardial infarction before hospital discharge; (2) 201T1 defects in more than one discrete vascular region, presence of delayed redistribution, or increased lung thallium uptake are more sensitive predictors of subsequent cardiac events than ST segment depression, angina, or extent of angiographic disease; and (3) low-risk patients are best identified by a single-region 201T1 defect without redistribution and no increased lung uptake.

Adult↗

The trace metal status of a group of post-menopausal vegetarians.

The copper, manganese, and selenium status of 36 post-menopausal vegetarians was compared with that of a group of post-menopausal omnivores, using dietary trace element intake data, serum and hair copper levels, and hair manganese and hair selenium levels as the principal indexes. Findings of this study suggest that the copper and selenium status of these long-term vegetarian women was comparable to that of non-vegetarians, despite the high intake of dietary fiber by the vegetarian group. In contrast, the manganese status of the vegetarians, as indicated by elevated hair manganese levels, was higher, almost certainly as a result of the significantly higher manganese intake of this group.

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