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Biomedical subjects

C Wolfe

Publications and source records attributed to C Wolfe.

At least 55 records · Page 3Linked to original sources
PubMed1989

Demarcation of myocardial ischemia: magnetic susceptibility effect of contrast medium in MR imaging.

Dysprosium diethylenetriamine-pentaacetic acid-bis (methylamide) (DTPA-BMA), a new nonionic contrast medium for magnetic resonance (MR) imaging, produces signal loss on T2-weighted images because of induced magnetic field gradients. The potential of this agent to delineate myocardial ischemia was investigated in 10 rats with acute (30 minutes) occlusion of the left coronary artery. T2-weighted MR images were acquired before and for 1 hour after intravenous administration of 1 mmol/kg of Dy-DTPA-BMA. Before administration of the contrast medium, signal intensity (SI) in the ischemic region was significantly greater than that in the normal myocardium; however, the borders of the ischemic region were not consistently distinct. The contrast medium caused marked decrease in SI of normal myocardium (18% +/- 3% of the control value), only slight decrease in the jeopardized region (76% +/- 6% of the control value), and no discernible effects on heart rate or blood pressure. Substantial contrast between normal and ischemic myocardium persisted for 1 hour. Moderate signal loss was observed in skeletal muscle. Dy-DTPA-BMA has the potential to demarcate the myocardial area in jeopardy as a region of high signal intensity because it erases signal preferentially in the normal myocardium.

Animals↗
PubMed1987

Ventricular septal defect: visualization of shunt flow and determination of shunt size by cine MR imaging.

Cine MR imaging is a new, fast technique that employs low flip angles, short repetition and echo times, and gradient-refocused echoes. This technique was used in three patients with documented ventricular septal defects (VSDs) to obtain transverse and oblique sections of the heart spanning the cardiac cycle. In all patients, cine MR imaging showed high-velocity turbulent blood flow across the defect as areas of low signal intensity extending from the left ventricle to the right ventricle. In the oblique sections oriented parallel to the interventricular septum it was possible to identify the cross-sectional area of the VSD. Quantification of the left-to-right shunt was performed by comparing left and right ventricular stroke volumes determined from end-diastolic and end-systolic volumes of both ventricles. Cine MR imaging provides important functional information and anatomic detail in patients with VSD and may be useful for diagnosis, determination of severity, and noninvasive monitoring of the disease.

Coronary Circulation↗
PubMed1986

NADPH binding induced proton ionization as a cause of nonlinear heat capacity changes in glutamate dehydrogenase.

Functional group interactions involved in the formation of the glutamate dehydrogenase-NADPH binary complex have been studied by three independent but complementary approaches: the pH dependence of the overall dissociation constant measured by an improved differential spectroscopic technique; the pH dependence of the enthalpy of complex formation measured by flow calorimetry; and the pH dependence of the number of protons released to, or taken up from, the solvent in the complex formation reaction, measured by titration. We conclude that the coenzyme binds to the enzyme through three distinguishable interactions: a pH-independent process involving the binding of the reduced nicotinamide ring; a relatively weak "proton-stabilizing" process, occurring at low pH involving the shift at a pK of 6.3 in the free enzyme to 7.0 in the enzyme-NADPH complex; and a stronger "proton-destabilizing" process, occurring at a higher pH involving a shift of a pK of 8.5 in the enzyme down to 6.9 in the enzyme-NADPH complex. The proton ionization of the free enzyme involved in this third interaction exhibits some unusual thermodynamic parameters, having delta Go = +11.5 +/- 0.1 kcal mol-1, delta Ho = +19 +/- 1 kcal mol-1, and delta So = +23 eu. We show here that this proton ionization step is directly related to and indeed constitutes the "implicit" shift in enzyme macrostates which we have shown to be responsible for the existence of large highly nonlinear delta Cpo effects in the formation of this complex [Fisher, H. F., Colen, A. H., & Medary, R. T. (1981) Nature (London) 292, 271-272].

Animals↗
PubMed1985

Early positive technetium-99m stannous pyrophosphate images as a marker of reperfusion after thrombolytic therapy for acute myocardial infarction.

Fourteen patients with transmural acute myocardial infarction (AMI) were treated with intravenous streptokinase a mean of 4 +/- 1 hours after chest pain and underwent technetium-99m stannous pyrophosphate (Tc-99m-PPi) imaging 7 +/- 2 hours after the onset of chest pain. The early Tc-99m-PPi images were obtained to test the hypothesis that an early, strongly abnormal Tc-99m-PPi image suggests reperfusion. Eleven of 14 patients had early peaking (within 16 hours) serum creatine kinase isoenzyme levels (CK-B) at a mean of 11 +/- 3 hours. Ten of 14 patients had 3+ or 4+ acute Tc-99m-PPi images. Eight of 11 patients had patent infarct-related vessels at cardiac catheterization 15 days after AMI. One patient who had both an early positive Tc-99m-PPi image and CK-B peak level had an occluded infarct-related artery at catheterization. Acute left ventricular (LV) ejection fraction (EF) by radionuclide ventriculography was compared with LVEF on day 15, and improved from 0.37 +/- 0.13 to 0.50 +/- 0.16 (p = 0.004) in the 10 patients with strongly positive acute Tc-99m-PPi images. LVEF also improved from 0.37 +/- 0.12 to 0.49 +/- 0.15 (p = 0.003) in the 11 patients with early peaking serum CK-B values. Three patients without evidence of reperfusion failed to improve the LVEF from the initial value to the one obtained at hospital discharge. Six control patients had acute Tc-99m-PPi images 10 +/- 2 hours after chest pain; none had strongly positive acute Tc-99m-PPi images, and the mean time to peak CK-B was 19 +/- 5 hours.(ABSTRACT TRUNCATED AT 250 WORDS)

Cardiac Catheterization↗
PubMed1982

Continuous noninvasive monitoring of left ventricular function during exercise by thoracic impedance cardiography-automated derivation of systolic time intervals.

Systolic time intervals (STI) obtained during exercise are useful as a method of estimating global left ventricular function. The conventional method, however, which requires a carotid pulse tracing as well as a phonocardiogram of high quality, is technically difficult under conditions of exercise. We have validated a new method of obtaining STI which employs the first derivative of thoracic electrical impedance (DZ/DT). The DZ/DT was recorded using surface electrodes and a microcomputer for automated signal processing. The new method was studied in 20 male normal subjects (aged 18 to 53 years) at rest and during increasing levels of upright exercise. Heart rate ranged from 61 to 173 beats/min. Results obtained simultaneously by both techniques showed no significant difference. Thus impedance cardiography allows continuous monitoring of STI during exercise and may prove to be a valuable addition to multistage stress testing.

Adolescent↗
PubMed1982

Pulsus alternans determined by biventricular simultaneous systolic time intervals.

This investigation was performed to determine the presence of unilateral or bilateral pulsus alternans in the systemic and pulmonary circulations in heart failure and to estimate the prevalence of pulsus alternans in congestive cardiomyopathy. The subjects were 36 adult patients in heart failure due to a variety of cardiopulmonary diseases. We measured left- and right-sided systolic time intervals from simultaneous dual echocardiograms of both semilunar valves. The alternans was left-sided in seven patients, right-sided in one patient and bilateral in six patients. Pulsus alternans was induced by ventricular premature complexes (VPCs), except in one patient with bilateral and persistent alternans. For a VPC to precipitate alternans, the early beat itself must be associated with an abbreviated ejection time. Echophonocardiographic records of 100 patients with congestive cardiomyopathy were reviewed for evidence of pulsus alternans. We found persistent alternans in 10 patients and VPC-induced alternans in seven patients. We could not measure any difference in severity of disease in patients with pulsus alternans compared with those without.

Adult↗
PubMed1980

Right ventricular myxoma. Case report and review of phonocardiographic and auscultatory manifestations.

Tumors in the right ventricle are extremely rare. This report concerns the pathogenesis of physical signs resulting from a right ventricular myxoma. In systole a loud midsystolic murmur representing outflow obstruction was present. In diastole a prominent vibration was heard and recorded. By echophonocardiography this noise could be ascribed to sudden halting of the retrograde excursion of the mass into the right ventricle--a mechanism analogus to the tumor "plop" associated with the halting of antegrade movement of a left atrial myxoma in the left ventricle in early diastole.

Adolescent↗
PubMed1980

Early aortic valve closure in combined idiopathic hypertrophic subaortic stenosis and discrete subaortic stenosis.

A patient with idiopathic hypertrophic subaortic stenosis (90 mm Hg resting intraventricular gradient) and discrete subaortic stenosis was found to have two separate systolic closing movements of the aortic valve on M mode echocardiography, each movement being associated with a separate systolic ejection murmur. The first closing movement occurred early in systole and was attributed to alterations in flow across the discrete stenosis. The second closing movement coincided with a later systolic murmur and systolic anterior motion of the mitral valve. The case supports the concept that timing of early closing movements of the aortic valve is useful in the diagnosis of subvalvular obstruction.

Adolescent↗
PubMed1980

Non-invasive diagnosis of subpulmonary outflow tract obstruction.

We have studied the echocardiographic and phonocardiographic findings in 18 patients with obstruction to ventricular outflow at subpulmonary valve level. The aetiology was congenital in 13 patients, a result of hypertrophic cardiomyopathy in three, and infiltration of the right ventricular outflow tract by glycogen or lymphoma in the remaining two. Abnormal systolic motion of the pulmonary valve, fluttering, and early or midsystolic closure were seen in 16 of 17 patients in whom the cusps were visualised. Normal pulmonary valve motion was found in one patient with coexisting pulmonary valve stenosis. In congenital infundibular stenosis the delay of the pulmonary component of the second heart sound (P2) was related to the severity of the obstruction. A pulmonary ejection sound, defined as a high-frequency sound occurring at the moment of full pulmonary valve opening, was absent except in the patient with coexisting pulmonary valve stenosis. In hypertrophic cardiomyopathy with obstruction to the right ventricular outflow, the ejection systolic murmur was softer with inspiration, a finding that contrasts with the respiratory variation seen with fixed obstruction. Recognition of these abnormalities should allow an accurate non-invasive diagnosis to be made and permit assessment of severity when P2 can be recorded.

Adolescent↗
PubMed1978

Musculocutaneous nerve injury after heavy exercise.

Three cases of musculocutaneous nerve injury distal to its innervation of the coracobrachialis muscle are reported. The syndrome typically features painless weakness of the biceps brachii and brachialis muscles, sensory loss in the distal volar forearm, a history of recent vigorous upper extremity resistive exercise, and resolution of the problem on resting the affected extremity. In all three reported cases the dominant arm was involved. The condition should not be confused with C-5 or C-6 radiculopathy, brachial plexopathy, or rupture of the biceps brachii muscle belly or tendon.

Adult↗
PubMedDate not supplied

Valuable lessons.

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Adaptation, Psychological↗
PubMedDate not supplied

Amino acid sequences which promote and prevent the binding and membrane insertion of surface-active peptides: comparison of melittin and promelittin.

The temporal sequence of molecular events involved in the interactions of a number of related peptides with membranes are revealed using two complementary fluorescence techniques. Comparative studies are reported of the interactions of melittin, promelittin and a melittin analogue with trp-19 replaced with Ile and the n-terminal gly replaced with a trp residue, with phosphatidylcholine membranes. It is shown that the interaction of the n-terminal region of melittin rapidly binds and inserts into the body of the membrane with a rate constant of around 367 s-1. This is followed by a slightly slower membrane insertion of the trp-19 region with a rate constant of around 112 s-1. The positive charges of the melittin molecule then come into close proximity with the membrane with rate constants around 27 s-1. Finally, these charged regions insert into the hydrophobic core of the membrane with rate constants of about 0.3 s-1. The effect of incorporating net negative charge onto the membrane surface in the form of 15 mole % phosphatidylserine, augments by about threefold, the binding of the charged domains of the melittin molecule. The observations of the melittin interactions are compared with the melittin-precursor protein, promelittin. Sections of the promelittin molecule are also found to bind and insert into the body of the phospholipid membrane, although nearly 30 times less rapidly than melittin. No charged sections of promelittin are found to insert into the membrane.

Amino Acid Sequence↗
PubMedDate not supplied

Stroke registers: a way to improve care.

The authors describe their continued involvement in a research project to assess the incidence, case-fatality and management of stroke in three health authorities of Southern England. The article focuses on how the findings of their research have been used in two of the districts, and the role research can play in beginning to improve the services for people who have had strokes.

Cerebrovascular Disorders↗