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Biomedical subjects

R Roberts

Publications and source records attributed to R Roberts.

At least 379 records · Page 21Linked to original sources
PubMed1988

First-pass radionuclide angiography using a multiwire gamma camera and tantalum-178.

A portable multiwire gamma camera (MWGC) with enhanced imaging characteristics relative to conventional sodium iodide camera has been evaluated with 178Ta, a short-lived, generator-produced radioisotope (half-life 9.3 min). First-pass radionuclide angiography (FPRA) was performed and results were compared to those obtained with FPRA using a multicrystal camera (MCC) and 99mTc in 38 patients. The overall left ventricular count sensitivity (counts/mCi/sec/millisteradians [msr]) was significantly higher with MWGC/178Ta (176 +/- 132 versus 108 +/- 49, p less than 0.001) yielding images of higher statistics with higher resolution collimation (31 versus 63 msr). Left ventricular ejection fraction was 0.54 +/- 0.18 by MWGC and 0.54 +/- 0.18 by MCC with an excellent correlation between the two techniques (r = 0.94, s.e.e. = 0.06). The detection of wall motion abnormality was virtually identical with the two techniques. Intra- and interobserver reproducibility by MWGC was excellent (r = 0.99 and 0.99, respectively). Thus, this new technology provides first-pass studies of higher statistical quality and improved resolution, affording more precise assessment of left ventricular performance and likelihood of further substantial improvement by use of even higher doses of 178Ta.

Adult↗
PubMed1987

In vivo assessment of vascular dilatation during percutaneous transluminal coronary angioplasty.

Previous studies of the mechanism of percutaneous transluminal coronary angioplasty used either postmortem specimens or animal models. To characterize the process of vascular dilatation in vivo, a system was devised for recording the instantaneous pressure-volume changes in the angioplasty balloon during inflation within the stenosed artery. The pressure-volume patterns obtained were compared with those observed in vitro with the balloon inflated in materials whose properties simulate stretching (Silastic tubing), compaction (styrofoam) and cracking (dry macaroni). Of 48 narrowings in 46 patients, a pressure-volume pattern of stretching was observed in 56%, compaction in 27% and cracking in only 17%. Of lesions manifesting a stretching pattern, 85% were longer than 5 mm cr had visible calcium deposits, whereas those that compacted were shorter and lacked calcium deposits. Both of these pressure-volume patterns were associated with a successful clinical outcome. Of 8 lesions exhibiting a cracking pattern, 6 showed dissection angiographically; 3 of these resulted in vessel occlusion.

Angioplasty, Balloon↗
PubMed1987

Effect of symptomless bacteriuria in childhood on subsequent pregnancy.

The outcome of 52 pregnancies in 34 women who had had bacteriuria in childhood was compared with that of normal control pregnancies. The prevalence of bacteriuria at the first antenatal visit was significantly higher (p less than 0.001) in previously bacteriuric women (35%) than in controls (5%), and acute pyelonephritis developed in 10% compared with 4% of controls. Pre-eclampsia (arterial pressure above 140/90 mm Hg with proteinuria above ++) developed in 4 of 12 previously bacteriuric women known to have renal scarring (5 of 16 pregnancies), in only 1 of 22 previously bacteriuric women without scars (1 of 36 pregnancies), and in 1 of 52 controls (p less than 0.001). Women with renal scars were also more likely to undergo induction of labour (44% of pregnancies) and operative delivery (57% of pregnancies) than previously bacteriuric mothers without scars (17%, 22%) or control mothers (16%, 20%). The infants of previously bacteriuric mothers were not significantly smaller than those of healthy control mothers, but Apgar scores were lower among offspring of previously bacteriuric mothers with scarred or normal kidneys (p less than 0.001). Fetal outcome was, however, satisfactory in all cases.

Adult↗
PubMed1987

A hemodynamic load in vivo induces cardiac expression of the cellular oncogene, c-myc.

To establish whether a hemodynamic load that causes cardiac hypertrophy in the intact animal might interact with cellular pathways that are thought to transduce growth signals in model systems, we have analyzed expression of the cellular oncogene, c-myc, after a systolic pressure load. Aortic constriction increased c-myc mRNA abundance in both the atria and left ventricle of 28-day rats, but did not activate a second "competence" gene, r-fos, whose expression by cardiac cells ceases upon termination of mitotic growth. In 80-day rats, c-myc was induced in the atria alone. Induction of c-myc by aortic constriction in vivo may correlate with the respective capacity of atrial and ventricular myocytes to replicate DNA during cardiac hypertrophy. Activation of c-myc was not sufficient to account for inhibition of muscle creatine kinase (mck) mRNA, which was decreased only in 28-day rats.

Aging↗
PubMed1987

Prognostic significance and beneficial effect of diltiazem on the incidence of early recurrent ischemia after non-Q-wave myocardial infarction: results from the Multicenter Diltiazem Reinfarction Study.

Of 576 patients with non-Q-wave acute myocardial infarction enrolled in the Diltiazem Reinfarction Study, 246 (43%) had 1 or more episodes of angina at rest or with minimal effort during 10.5 days of treatment with either diltiazem (90 mg every 6 hours) or placebo. Reinfarction (12.2% vs 3.6%, p less than 0.0001) or death (6.1% vs 1.5%, p = 0.003) was more likely to occur within 2 weeks of randomization in patients with postinfarction angina than in those without angina. Based on serial electrocardiographic data, 115 of the 246 patients with angina had transient ST-T changes and 131 did not. Comparison of the 14-day event rates in these 2 groups showed that the 115 patients with electrocardiographic evidence of ischemia had a higher frequency of reinfarction (20% vs 5.3%, p less than 0.001), more extensive damage as assessed by peak MB-creatine kinase levels (91 +/- 76 vs 37 +/- 19 IU/liter, p = 0.059 [Wilcoxon rank sum]) and a higher mortality rate (11.3% vs 1.5%, p = 0.001). Angina associated with transient ST-T changes occurred in 70 of the 289 patients in the placebo group but in only 45 of the 287 patients in the diltiazem group--a 28% reduction in cumulative life-table incidence (p = 0.0103 [2-tail, log rank]; 95% confidence interval, 9.3 to 53.8%). It is concluded that patients with early postinfarction angina are at increased risk of reinfarction and death, and angina associated with transient electrocardiographic changes identified a very high risk subset. This subset appeared to have a larger area of viable but jeopardized myocardium and benefited from prophylactic therapy with diltiazem.

Actuarial Analysis↗
PubMed1987

Peak creatine kinase as a measure of effectiveness of thrombolytic therapy in acute myocardial infarction.

As part of the National Heart, Lung, and Blood Institute multicenter Thrombolysis in Myocardial Infarction Trial, the time to peak plasma creatine kinase (CK) activity as a marker of reperfusion in 272 patients with validated acute myocardial infarction was analyzed. Patients were treated with either tissue-type plasminogen activator or streptokinase by intravenous administration. All patients underwent acute coronary angiography. The infarct-related artery was identified and thrombolytic therapy administered. Reperfusion at 90 minutes was documented by angiography. CK was determined before institution of therapy and every 4 hours thereafter for the first 24 hours. Patients were classified into 3 groups for comparative purposes: group 1--occlusion with no reperfusion (n = 119); group 2--occlusion with reperfusion (n = 98); and group 3--subtotal occlusion (n = 55). Early (within 4 hours after treatment) and late (more than 16 hours after treatment) peaking of CK differentiated patients with drug-induced perfusion from those without reperfusion. Although peak CK between 5 and 11 hours after drug treatment did suggest perfusion through the infarct-related artery, it did not differentiate between drug-induced and spontaneous reperfusion. Clinically, early peak CK is a useful noninvasive means of assessing coronary artery patency. However, in clinical trials assessing drug therapy, the use of peak CK may overestimate drug effectiveness by including patients with spontaneous reperfusion.

Angiography↗
PubMed1987

Human creatine kinase: isolation and sequence analysis of cDNA clones for the B subunit, development of subunit specific probes and determination of gene copy number.

cDNA clones for human B creatine kinase were isolated from human brain and placenta libraries. The entire coding and 3' untranslated regions, as well as 23 bp of the 5' untranslated region were sequenced. Complete sequence identity was found among the clones, with the exception of an area of heterogeneity among the 3' untranslated region of the brain and placenta clones. A 77.7% nucleotide sequence identity was found between the coding region of human B creatine kinase and our previously reported human M creatine kinase. In contrast, no homology was found in the 3' untranslated regions. Probes were constructed from the nonconserved 3' untranslated regions of human M and B creatine kinase and were shown to be highly specific. Southern transfers of total genomic DNA derived from human placenta and digested to completion with several restriction enzymes were probed with the MCK and BCK specific probes producing single hybridization bands. These results suggest that creatine kinase M and B are single copy genes in the human genome.

Amino Acid Sequence↗
PubMed1987

A controlled trial of teaching critical appraisal of the clinical literature to medical students.

We carried out a controlled trial of teaching the critical appraisal of clinical literature among final-year clinical clerks. Tutors at two of four teaching hospitals were offered a short course in the critical appraisal of clinical articles that describe diagnostic tests and treatments and were assisted in identifying and appraising specialty-specific articles that described those diagnostic tests and treatments that clinical clerks were sure to encounter during their clerkship tutorials. Tutors and clerks at the other two hospitals received no special intervention and served as controls. Experimental and control clinical clerks completed pretests and posttests of their ability to take and defend a stand on whether to apply specific diagnostic tests and treatments in specific clinical situations. Experimental clerks demonstrated both statistically and "clinically" significant increases in their critical appraisal skills, improving 37% on the diagnostic test exercise and 8% on the treatment exercise; control students' scores deteriorated for both.

Clinical Clerkship↗
PubMed1987

Electrocardiographic evolution of posterior acute myocardial infarction: importance of early precordial ST-segment depression.

Precordial ST-segment depression is typically observed in anterior non-Q-wave acute myocardial infarction (AMI), and is generally not regarded as an indication for acute thrombolytic therapy. Of 544 patients with creatine kinase (CK)-MB-confirmed non-Q-wave AMI randomized to the prospective multicenter Diltiazem Reinfarction Study, 50 patients (9.2%) had isolated precordial ST-segment depression of 1 mm or more in 2 or more contiguous precordial electrocardiographic leads (V1-V4). Serial electrocardiograms recorded at study entry (mean 50.5 hours after onset of chest pain), on study day 2, study day 3 and at predischarge showed that in 23 of 50 patients (40%) electrocardiographic evidence of posterior AMI evolved, defined as an R wave of 0.04 second or more in lead V1 and an R:S greater than or equal to 1 in lead V2. In 18 of these 23 patients (78%), posterior AMI had evolved by study day 3, and none had an abnormal reelevation of CK-MB (every 12-hour sampling) for up to 14 days of hospitalization. Compared with the remaining 27 patients who had electrocardiographic features of anterior non-Q-wave AMI only, the 23 with initial precordial ST segment depression in whom posterior AMI developed had significantly higher mean peak CK values (1,051 +/- 172 vs 663 +/- 89 IU, p less than 0.009) and greater mean precordial ST-segment depression in lead V1 (0.28 vs + 0.19 mm, p = 0.01), in lead V2 (1.3 vs 0.26 mm, p = 0.003) and in lead V3 (2.0 vs 0.93 mm, p = 0.0004).(ABSTRACT TRUNCATED AT 250 WORDS)

Creatine Kinase↗
PubMed1987

Cytomegalovirus retinitis in rheumatic disease: a case report.

We describe a 67-year-old white man with Wegener's granulomatosis who was treated with cyclophosphamide, then with azathioprine, and who subsequently developed cytomegalovirus retinitis. The patient initially improved on a course of adenine arabinosine, but his retinitis has progressed, despite discontinuation of immunosuppressive therapy. We show that cytomegalovirus retinitis does occur in patients with rheumatic diseases who receive immunosuppressive therapy.

Adult↗
PubMed1987

Clinical pharmacology and therapeutics education for senior medical students.

In many medical schools instruction of students in clinical pharmacology remains informal and may be inadequate. To determine the short-term efficacy of a mandatory senior medical year course in clinical pharmacology, we compared examination scores of senior students in the College of Medicine, University of Iowa, either prior to or following the Clinical Pharmacology and Therapeutics Lecture Series. A significantly higher (P less than .001) mean score was demonstrated by students taking the examination following the course (75 +/- 4% correct) versus those taking the examination prior to the course (55 +/- 4% correct). To determine student acceptance, postcourse questionnaires were completed. Students surveyed immediately postcourse and alumni surveyed up to four years after graduation highly recommended the course and favored retaining it as a mandatory part of the fourth-year curriculum. This study confirms the efficacy and acceptance of senior medical courses in therapeutics and suggests an effective role for clinical pharmacologists in their design and execution.

Curriculum↗
PubMed1987

Production of and response to growth-stimulating activity in isolated bone cells.

Autologous growth-promoting activity has been shown to be secreted by bone organ cultures. To identify the cellular source of these growth factors, we have studied the activity present in cell extracts prepared from isolated bone cells released early or late from mouse calvariae following collagenase digestion. Previous studies have established that early released cell populations reside on the bone surface and consist of a heterogeneous mixture of cells that are less osteoblastic than late released cells. We find that soluble extracts of the latter cells contain more growth-promoting activity/mg of cellular protein than those of the former. By this criterion late released cells appear to be the major source of endogenous growth factors. On the other hand, upon exposure to bone cell-derived cell extracts, early released cells express a greater-fold increase in [3H]thymidine incorporation into acid insoluble radioactivity than late released osteoblasts because of the high basal mitogenic activity of the latter which may be related to their production of autologous growth factor. These data suggest that both early and later released cells may be major targets for bone growth factors produced in situ by late released osteoblasts.

Animals↗
PubMed1987

Tissue interactions and measurement of ablation rates with ultraviolet and visible lasers in canine and human arteries.

Ablation rates measured as the depth of tissue excavation per unit time were determined in human and canine aortas subjected to radiation with ultraviolet (UV) excimer (ArF 193 nm, KrF 248 nm, XeF 351 nm) and visible lasers [continuous wave (cw) and 50-ms chopped argon ion, 478 nm-514 nm; pulsed double-frequency Nd:YAG, 532 nm]. For UV and pulsed double-frequency Nd:YAG lasers ablation rates were constant in time and depended linearly on average laser power, but for cw and chopped argon lasers ablation rates varied with irradiation time and were nonlinearly dependent on laser power. In human aortas, atherosclerosis without gross calcification had no influence on ablation rates. Charring and tissue disruption were observed with cw and chopped argon ion, whereas excimer and pulsed Nd:YAG lasers produced only minimal injury to surrounding tissue. We conclude that the determination of ablation rates is useful for the selection of laser wavelengths and power densities applicable to angioplasty and that UV and pulsed visible laser permit a better control of ablation compared to continuous wave lasers.

Animals↗
PubMed1987

Asymptomatic telephone ECG transmissions as an outpatient surveillance system of ventricular arrhythmias: relationship to quantitative ambulatory ECG recordings.

Although ambulatory ECG recordings provide quantitative information in the follow-up of patients with ventricular arrhythmias, they are performed infrequently, potentially missing serious arrhythmias in the unmonitored periods. Telephone ECG systems offer "real-time" ECG information, theoretically functioning as an arrhythmia surveillance system. Thus we incorporated frequent telephone ECG transmissions in two antiarrhythmic drug protocols. The first investigation was designed to show the relationship of telephone and ambulatory ECGs in patients with frequent ventricular tachycardia (VT). The second protocol selected patients with "nonlife-threatening" frequent premature ventricular complexes (PVCs) in whom a second placebo period was instituted to simulate the clinical situation of asymptomatic arrhythmia increase. In both drug trials there was a strong linear relationship between the log-transformed PVC counts of telephone ECG and concomitant PVC, couplet, and VT frequencies on ambulatory ECG. In the VT population, greater than or equal to 1 PVC on telephone ECG reflected the presence of VT on ambulatory ECG (sensitivity 87%; specificity 77%). In the second study, telephone ECG transmissions with PVCs on three consecutive transmissions reflected the change from less than or equal to 10 PVCs/hour to greater than or equal to 40 PVCs/hour on ambulatory ECG within 48 hours. These data support the concept that daily surveillance by means of telephone ECG provides arrhythmia information of qualitative clinical relevance.

Ambulatory Care↗
PubMed1987

Dissociation between global and regional systolic and diastolic ventricular function during coronary occlusion and reperfusion.

Indexes of global ventricular function such as the ejection fraction (EF) and the peak diastolic filling rate (PDFR) are often used to assess the effects of coronary recanalization in patients with myocardial infarction. In this investigation we assessed the relationship between these global indexes and directly measured indexes of regional function during 15 minutes of coronary occlusion followed by 120 minutes of reperfusion in 22 open-chest dogs. A computerized nuclear cardiac probe was used to assess EF and PDFR. Indexes of regional function were measured by Doppler ultrasonic wall-thickening probes. During coronary occlusion, paradoxical systolic thinning occurred and the EF and PDFR decreased an average of 31.6% and 24.4%, respectively. During reperfusion the EF and PDFR improved rapidly and at 60 minutes were similar to baseline. Systolic wall thickening improved more gradually and remained abnormal throughout reperfusion. Likewise, indexes of diastolic function (mean rate to half end-diastolic thinning and late diastolic thinning fraction) recovered slowly and remained abnormal throughout reperfusion (78% and 69.7%, respectively). The correlation between the rate of change of global and regional function was poor during both coronary occlusion and reperfusion. Thus, during coronary occlusion the global and regional indexes of ventricular function undergo directionally similar changes. However, during coronary reperfusion the global indexes do not reflect the slow recovery of the stunned myocardium.

Animals↗
PubMed1987

Effects of exercise tolerance, age, and gender on the specificity of radionuclide angiography: sequential ejection fraction analysis during multistage exercise.

We investigated the factors that determine the left ventricular ejection fraction response to exercise in 57 middle-aged, untrained patients with angiographically normal coronary arteries. The ejection fraction was measured by blood pool radionuclide angiography during each stage of exercise. Stepwise regression analysis was applied to 39 variables, and the resulting significant variables were then included in a logistic regression model to determine which of them would predict a normal ejection fraction response. By stepwise regression analysis, the best model (F = 5.6, p = 0.0004) was obtained by combining four variables: achieving 85% of maximal predicted heart rate, peak heart rate, number of exercise stages performed, and resting pulse pressure. Only the latter two variables were significant by logistic regression analysis. The specificity of greater than or equal to 5 ejection fraction unit increase at peak exercise was 42%, 75%, and 100% in patients who exercised one, two, or three stages, respectively. Furthermore, the increase in ejection fraction during each exercise stage was independent of age or gender. Thus the standard criteria of normality during exercise radionuclide angiography have high specificity only when applied to patients with good exercise performance, regardless of age or gender.

Adult↗
PubMed1987

The superior mesenteric artery fat plane: is obliteration pathognomonic of pancreatic carcinoma?

Obliteration of the fat plane surrounding the superior mesenteric artery has been described as characteristic of pancreatic carcinoma. To determine the specificity of this and other computed tomography findings in the pancreas and peripancreatic region, scans of 86 patients were reviewed without clinical history. Diagnoses included pancreatitis (26 patients); pancreatic adenocarcinoma (14 patients); lymphoma (17 patients); metastatic nonpancreatic carcinoma (14 patients); and normal findings (15 patients). Confluent adenopathy could not be reliably differentiated from a pancreatic mass except when adenopathy separated the common bile duct from the duodenum. Retrocrural adenopathy was unusual with pancreatic carcinoma. The fat plane surrounding the superior mesenteric artery was obliterated with pancreatic carcinoma (36%), nonpancreatic carcinoma (29%), and lymphoma (24%), but not with pancreatitis, although perivascular edema was seen in 19%. Evaluation of the celiac axis was less rewarding. Obliteration of the superior mesenteric artery fat plane is a sign of malignancy, but it is not specific for pancreatic carcinoma. We propose that the superior mesenteric artery origin be considered within a paraaortic space, separate from the anterior pararenal space. This explains its characteristic lack of involvement by pancreatitis.

Adipose Tissue↗