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Biomedical subjects

R A Mathews

Publications and source records attributed to R A Mathews.

At least 37 records · Page 2Linked to original sources
PubMed1982

A uridine adduct with an ester of the carcinogen 3-hydroxy-1-methylxanthine.

The structure of the uridine adduct with the acetate ester of the carcinogen 3-hydroxy-1-methylxanthine has been determined. Covalent binding is between C-8 of xanthine and O-2 of uracil. This was determined from studies of the NMR spectrum, mass spectra and solvolysis in liquid hydrogen sulfide. The nucleoside adduct, formed with uridine, is identical with the adduct with polyuridylic acid after enzymatic hydrolysis. Treatment with aqueous ammonia or pH 7 at 100 degrees C leads to the loss of ribose. Thymidine also forms an adduct with 3-acetoxy-1-methylxanthine in a similar yield. Model studies with a space-filling model suggest that the methylxanthine moiety can fit into the major groove of DNA and cause minimal helix distortion if the thymine base is rotated into the unnatural syn conformation.

Chemical Phenomena↗
PubMed1982

Blade atrial septostomy: collaborative study.

During the past 4 years, five institutions have collaborated in evaluating the efficacy of blade atrial septostomy. The procedure was performed in 52 patients, including 31 with transposition of the great arteries, 10 with mitral atresia, five with tricuspid atresia and six with miscellaneous anomalies. The patient's ages ranged from 1 day to 12 years (mean 13 months). Improvement occurred in 41 of 52 patients (79%). Four patients had an intact interatrial septum, and blade atrial septostomy was successfully performed by a transseptal technique. One patient died from a lacerated left atrial wall; other complications occurred in four patients. Blade atrial septostomy is an effective palliative procedure, even when the interatrial septum is thickened or intact.

Arteries↗
PubMed1980

Coarctation of the aorta in children. Late results after surgery.

From 1960 to 1970, 110 patients underwent operation for coarctation of the aorta. The overall mortality was 23%. However, in infants operated on at less than 6 months of age, the mortality was 63%, whereas there was only a 4% mortality in those operated on after 6 months of age. Late follow-up was available in 87 patients from five to 15 years postoperatively. There was a 14% frequency of recoarctation in the group of long-term survivors. Systemic hypertension, defined as an upper extremity blood pressure greater than 140/90 mm Hg, was found in 23% of the survivors. This study has demonstrated a significant frequency of postcoarctectomy hypertension and residual hemodynamic and angiographic abnormalities in patients without clinical evidence of recoarctation. This indicates the need for continued long-term follow-up of these patients.

Adolescent↗
PubMed1980

Absent right superior vena cava with persistent left superior vena cava: implications and management.

Seven cases of absent right superior vena cava with persistent left superior vena cava and normal situs were diagnosed at Children's Hospital of Pittsburgh. All patients had associated cardiac defects. In two cases the diagnosis was made at autopsy, the first in 1957 and in a 26 day old infant with multiple cogenital defects and the second in 1965 in a 22 day old infant who had pulmonary atresia with ventricular septal defect and patent ductus arteriosus. Since 1966 absent right superior vena cava has been diagnosed at cardiac catheterization in five children. Three of these children have had surgery, two for subaortic stenosis and one for an atrial septal defect. One has an insignificant atrial septal defect and the fifth has a ventricular septal defect. The electrocardiogram of four reveals s short P-R interval and a leftward frontal plane axis of the P wave, suggesting a low atrial focus. None has had any significant conduction problem. All five children are living and well, the oldest has survived 13 years postoperatively. Certain precautions are necessary should corrective cardiac surgery or transvenous pacemaker insertion be necessary.

Adolescent↗
PubMed1980

Carcinogenic purine N-oxide ester modifies covalently all common bases in polynucleotides.

The carcinogen 1-methyl-3-hydroxyxanthine after esterification binds covalently to polynucleotides, RNA and DNA. All four ribopolynucleotides and poly(dT) are targets. Depending on reaction conditions, covalent binding is greatest to poly(A) followed by poly(U), poly(dT), poly(G), poly(C), RNA and DNA. Maximal covalent modification of DNA is one moiety per 360 nucleotides. All modified polynucleotides, RNA and DNA, except poly guanylic acid have been enzymatically digested and the major adducts characterized as nucleosides.

Binding Sites↗
PubMed1980

Electrocardiogram in double chamber right ventricle.

Thirty patients with a double chamber right ventricle were seen during a 7 year period. The majority of patients had associated cardiac anomalies, most commonly a ventricular septal defect. In this series, as in others, the history, clinical examination, chest roentgenogram and echocardiogram were inconclusive for diagnosing double chamber right ventricle. Symptoms were generally related to the severity of the associated anomalies. In 40 percent of the patients reviewed, upright T waves were found in lead V3R as the only electrocardiographic finding suggestive of right ventricular hypertrophy. Because upright T waves in lead V3R in the absence of other evidence of right ventricular hypertrophy are not commonly seen in patients with an isolated ventricular septal defect or a defect associated with other forms of right ventricular outflow obstruction, this finding should alert the cardiologist to the possibility of the presence of double chamber right ventricle prior to cardiac catheterization.

Adolescent↗
PubMed1979

Cytochrome c peroxidase. Interconversion of chemically and enzymatically reactive and unreactive forms of the ferric protein.

Ferric yeast cytochrome c peroxidase in the presence of different anions may assume a number of forms which differ in optical spectra and chemical properties. In solutions whose only anion is acetate, two spectral forms are present together in an equilibrium. Each of these spectral species is believed to bear bound acetate anion. A form characterized by an intense absorption maximum at 620 nm is unreactive enzymatically and does not react with hydrogen peroxide or with dithionite. A form characterized by a less intense absorption near 645 nm is enzymatically and chemically reactive. Increasing temperature and increasing pH displace the equilibrium toward the 645 nm form. Increasing cytochrome c peroxidase concentration favors the 620 nm form. In kinetic experiments in which the 645 nm form is removed by rapid reaction with H2O2 or dithionite, the 620 nm form is converted in a first order reaction (k = 0.36 s-1, 15 degrees C) to the 645 nm form. In solutions whose sole anion is phosphate a 645 nm form is the only demonstrable spectral species. The enzymatic activity and rates of chemical reaction of 645 nm spectral forms occurring in acetate and in phosphate buffers are the same.

Cytochrome-c Peroxidase↗
PubMed1979

Iliac venous thrombosis in infants and children after cardiac catheterization.

Twenty-two patients developed thrombosis of the lower abdominal portion of the inferior vena cava, iliac or femoral vein (IVT) after cardiac catheterization. All patients has at least one previous study from 1 day to 11 months of age (mean, 2 months) and seven had two catheterizations before discovery of IVT. Transposition of the great arteries was the most common defect associated with IVT (12/22, 55%). From one to seven catheter changes were made during the time of venous cannulation (mean, 105 minutes). No clinical evidence of IVT was present immediately after the preceding cardiac catheterization. The discovery of significant IVT usually necessitated the use of a vein from the upper extremity to complete the cardiac catheterization. IVT was associated with previous balloon atrial septostomy using either a Fogarty or Rashkind septostomy catheter in 13/22 patients (59%). In addition, 86% of the patients had either of these balloon catheters or a Swan-Ganz catheter used during a previous study. The potential development of IVT should be considered especially in cyanotic infants and small children in whom balloon catheters are used.

Cardiac Catheterization↗
PubMed1979

Pneumonectomy for intractable left bronchial compression in d-transposition of the great arteries.

In infants with transposition of the great arteries (TGA) tracheobronchial obstruction may occur as a result of compression by a dilated posterior pulmonary artery, especially if there is a large interventricular septal defect with its attendant large pulmonary blood flow and high pressure. Banding of the pulmonary artery may give temporary relief. A patient with TGA had collapse of the left lung at 2 months of age, following atrial septectomy. Bronchoscopy and bronchography revealed extrinsic compression of the left main bronchus. Banding of the pulmonary artery at 6 months of age relieved the respiratory distress. At 8 years of age atelectasis of the left lung recurred following a Mustard procedure. Two additional procedures were attempted to decrease the pressure of the pulmonary artery on the bronchus but these were unsuccessful. At age 9 years, pneumonectomy, her sixth thoracotomy, was performed as a final attempt to relieve the respiratory problem caused by persistent atelectasis. She is now 17 years of age and has remained asymptomatic during the last 8 years.

Adolescent↗
PubMed1978

Echocardiographic and hemodynamic correlation in transposition of the great arteries.

Echocardiography was performed in 36 patients with transposition of the great arteries (TGA). Twenty patients were studied before a Mustard operation, 14 patients after operation and two patients both before and after operation. Right ventricular end-diastolic dimension (RVED) was larger than normal in each patient and tended to increase postoperatively. In contrast, the left ventricular end-diastolic dimension (LVED) was significantly reduced postoperatively in all patients. A linear relationship was demonstrated between the ratio of LVED/RVED and the ratio of peak systolic pressures in the left and right ventricles in studies both before and after Mustard operation. Systolic anterior motion of the mitral valve was observed in 18% of peroperative patients and increased to 44% postoperatively. The incidence of fluttering of the mitral valve increased from 50% to 94% after the operation. Abnormal septal motion was found in 39% of cases. Abnormal movement of the mitral valve and of the interventricular septum seems to be related to a reversed pressure relationship in the ventricles. Shifting of the ventricular septum toward the left ventricle and consequent distortion of the left ventricular cavity and mitral valve apparatus may be responsible for the abnormal echocardiographic findings. Serial echocardiographic studies may be useful as a noninvasive tool in the assessment of left ventricular pressure or the status of the pulmonary vascular bed in TGA.

Adolescent↗
PubMed1978

Left ventricular anomalies associated with Ebstein's malformation of the tricuspid valve.

Seventeen patients with Ebstein's malformation of the tricuspid valve have been evaluated. The majority of patients (11/17) presented in the newborn period with cyanosis and cardiomegaly. The remainder (6/17) were referred because of cardiomegaly on chest X-ray and/or a heart murmur heard on routine examination. Three patients have died; one in the newborn period and two suddenly at the age of 11 and 15 years. Thirteen patients have undergone right and left heart cardiac catheterization within the last seven years. Twelve of these 13 patients (92%) had angiocardiographic left ventricular contraction abnormalities. Five patients also had mitral valve prolapse associated with left ventricular dysfunction. Since many patients with Ebstein's anomaly may have significant left ventricular abnormalities, careful and systematic evaluation of the left ventricle is warranted.

Adolescent↗
PubMed1978

Clinical use of blade atrial septostomy.

A cardiac catheter enclosing an extensible blade was used to enlarge the interatrial opening in seven patients. Two patients with transposition of the great arteries who had balloon atrial septostomy as newborns subsequently presented with clinical evidence of a restrictive interatrial opening at 1 and 4 months of age. Cardiac catheterization confirmed restenosis of the interatrial opening and inadequate intracardiac mixing. After blade atrial septostomy the systemic arterial oxygen saturation increased by 20% and 30%, respectively. Five patients with mitral atresia complex, ages 2 months-9 1/2 years, had a restrictive interatrial communication and severe pulmonary venous hypertension (mean left atrial pressures ranged from 20-38 mm Hg). Following blade atrial septostomy, the pressure gradient between the atria was almost completely abolished and prompt clinical improvement was observed in each patient. All patients tolerated the procedure without complications. Blade atrial septostomy was a safe, effective procedure for enlarging the interatrial communication in this limited series of patients with an interatrial septum too thick to permit adequate rupture by conventional balloon atrial septostomy.

Age Factors↗
PubMed1978

Bilateral ductus arteriosus in d-transposition of the great arteries with right aortic arch.

The rare anomaly of a right aortic arch, distal origin of the left subclavian artery, and posterior left ductus arteriosus (forming a vascular ring) plus a right ductus arteriosus is described in an infant with d-transposition of the great arteries with an intact septum. The presence of a right aortic arch and distal left subclavian artery with bilateral ductus arteriosus has not been described previously.

Aorta, Thoracic↗
PubMed1978

Arrhythmias and Stokes-Adams attacks in acute rheumatic fever.

In spite of general complacency about first-degree heart block in acute rheumatic fever, abnormal conduction with dysrhythmias, occasional complete heart block, and, rarely, Stokes-Adams attacks are important early signs of acute rheumatic fever and may precede other signs. Every person with episodic fainting is entitled to an ECG, and frequent ECGs are imperative in any case of rheumatic fever with signs of arrhythmias. Changing atrioventricular block necessitates continuous monitoring for dysrhythmias. A 13-year-old boy who appeared with Stokes-Adams attacks secondary to acute rheumatic fever was successfully treated by temporary pacing.

Acute Disease↗