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Biomedical subjects

S Stewart

Publications and source records attributed to S Stewart.

At least 307 records · Page 17Linked to original sources
PubMed1982

Gene controlled negative regulation of DNA synthesis in erythropoietic progenitor cells.

Congenic strains differing by a small segment of Chromosome 9 that bears the Fv-2 locus have provided valuable material for investigating genetic resistance to Friend polycythemia virus (FV). C57BL/6 (B6) (Fv-2rr) mice have been found to differ from B6.S (Fv-2ss) mice not only in their response to this virus but also in the proliferative state of their erythropoietic progenitor cells BFU-E: in B6 mice the majority of BFU-E are normally quiescent, while in B6.S mice approximately 50% are actively synthesizing DNA at any time. We have shown that B6 but not B6.S marrow contains a macromolecule that negatively regulates DNA synthesis specifically of BFU-E in vitro. Evidence is presented that this macromolecule is a physiological negative regulator active in vivo in B6 mice. A new liquid culture system is described in which FV and erythropoietin (epo) act synergistically on Ficoll-Isopaque separated bone marrow cells to give rise after 7 days to large numbers of CFU-E detectable in 2-day plasma cultures with and without epo. Inclusion of concentrated B6 but not B6.S bone marrow supernatant in liquid cultures drastically curtailed the amplification of CFU-E by FV and epo. These studies indicate that both DNA synthesis and the BFU-E stage of differentiation are necessary conditions for initiating the effects of polycythemia-inducing FV. Genetic resistance to FV appears not to reside within the target cells for the virus.

Animals↗
PubMed1982

Clinical outcomes after inferior myocardial infarction.

We studied the clinical outcomes of 46 patients followed prospectively for the initial 6 months after inferior infarction. Twenty-one patients (Group A) had no anterior ST depression (V2 to V4) present during the acute phase of the inferior infarction, whereas 25 patients (Group B) had such findings transiently. Although the clinical course during hospitalization was similar in the two groups, that after discharge differed. Only one of 21 patients in Group A had exertional angina and none had rest angina during follow-up; no infarcts or deaths occurred. In contrast, 15 patients in Group B had exertional angina; 12 also had rest pain (p less than 0.001, exact probability test). Two patients had reinfarction, one of whom died, and one sudden death also occurred. Of 15 patients in Group B who had cardiac catheterization, only eight had significant lesions in the anterior vessels, whereas seven did not; six of the seven patients became asymptomatic during follow-up without surgical therapy. Thus, electrocardiograms taken during the early phases of inferior myocardial infarction may be a valuable tool to recognize patients likely to have further ischemic symptoms during the early follow-up period.

Angina Pectoris↗
PubMed1981

False aneurysm and pseudo-false aneurysm of the left ventricle: etiology, pathology, diagnosis, and operative management.

Four patients are presented in whom either a false aneurysm or a "pseudo-false" aneurysm of the left ventricle developed following a myocardial infarction. False aneurysms of the left ventricle are unusual and are distinctly different from the more common true aneurysms. A false aneurysm is the result of a contained hematoma dissecting, into a transmural infarct. It communicates with the left ventricle through a small orifice. Previous descriptions of false aneurysms have stressed that their wall consists of pericardium and mural thrombus and lack identifiable epicardial or myocardial elements. Two pseudo-false aneurysms are described. They communicated with the left ventricle through a small orifice but their wall contained myocardial tissue. False aneurysms have a tendency to rupture and therefore their presence alone is an indication for operation. One of the pseudo-false aneurysms discussed ruptured into the right ventricle. The operation for false aneurysm may be simpler than that for true aneurysm since it might be possible to close the small communication into the left ventricle without resecting the entire aneurysm wall.

Adult↗
PubMed1981

Coronary artery injury by a valved external conduit.

A 4-month-old infant underwent repair of type I truncus arteriosus and died immediately after as a consequence of left main coronary artery compression by the metallic stent in the Dacron conduit. To avoid injury to the coronary vasculature, the future location of the porcine valve ring should be assessed and relocated if necessary.

Bioprosthesis↗
PubMed1981

Copper metabolism and requirements in total parenteral nutrition.

Copper metabolism and requirements in patients receiving total parenteral nutrition were studied in 28 patients with gastrointestinal diseases. During each of the 3 wk of the study period, each of 24 patients received in their total parenteral nutrition solutions, a daily dose of copper amounting to 0.25 mg, 1.05 mg, or 1.85 mg, in a random order. The other 4 patients received a fixed daily dose of 1 mg throughout the 3 wk. Increased losses of copper through the gastrointestinal tract occurred in patients with diarrhea or high-output stomas or fistulas. Patients with abnormalities of liver excretory functions had decreases in gastrointestinal copper losses. Urinary copper excretion was twice that of normal subjects. Copper infused in excess of the requirements was retained and not excreted. Plasma copper did not reflect the copper balance and cannot be used as a guide for copper supplementation. Copper requirements were found to be 0.3 mg/day in patients with normal amounts of gastrointestinal excretion. In the presence of diarrhea or increased fluid loss through gastrointestinal stomas or fistulas, the copper requirements for total parenteral nutrition are 0.4--0.5 mg/day.

Adolescent↗
PubMed1981

Coexisting idiopathic hypertrophic subaortic stenosis and coronary artery disease. Clinical implication and operative management.

Patients with either coronary artery disease (CAD) or idiopathic hypertrophic subaortic stenosis (IHSS) may have angina as a dominant symptom. It is also possible that these two diseases may coexist in the same patient. Such an association has been reported in 25% of patients with IHSS who are over 45 years of age. It is important that both entities be looked for in the evaluation of the patient with angina, particularly when operative management is contemplated. Treatment of one and not the other may leave the patient symptomatic. We have encountered three patients with both CAD and severe IHSS and have managed each with septal myectomy and coronary artery revascularization. Each has obtained significant symptomatic improvement.

Aged↗
PubMed1980

Rhabdomyoma of the heart: a diagnostic and therapeutic challenge.

The sector scan was decisive in establishing the diagnosis of multiple rhabdomyomas of the heart in a newborn infant. Successful resection of the tumors was performed with profound hypothermia and limited cardiopulmonary bypass. Nine months later, the infant died of the complications of tuberous sclerosis. This case report documents the diagnostic accuracy of the sector scan and the potential benefit of aggressive surgical management of this condition.

Diagnosis, Differential↗
PubMed1979

Characterization of stem cells and progenitors of hemopoiesis by cell sorting.

Cell sorting has been used as a method for characterizing hemopoietic stem cells and progenitors. Fluorescent antibody-surface labels and changes in fluorescence polarization induced by in vitro stimulation with potential hemopoietic regulators were used. As detected by significant enrichment of CFU-S (pluripotent stem cells) in fluorescence-activated cell sorting, some CFU-S bear 'unique antigens' recognized by rabbit anti-human brain sera, human anti-human sperm sera, and 129 anti-F9 serum, but not A . TH anti-A . TL (Ia) ascites. Significant changes in fluorescence polarization induced by in vitro stimulation of mouse bone marrow with potential hemopoietic regulators were also observed; further, progenitors of human T-lymphocyte colonies were observed to exhibit a significantly decreased mean polarization value after short-term stimulation with PHA-LCM (phytohemagglutinin-stimulated leukocyte conditioned medium).

Animals↗
PubMed1979

Discontinuity between the heart and the pulmonary circulation. Its management with the use of a valved external conduit.

The Hancock conduit that contains a porcine xenograft valve has been used in part of the cardiac repair of 22 patients with complex congenital heart disease. Five patients had a severe form of tetralogy of Fallot; six had pulmonary atresia; five had transposition of the great vessels, ventricular septal defect (VSD), and pulmonic stenosis; five had truncus arteriosus; and one had "corrected" transposition, VSD, and pulmonic stenosis. The hospital mortality was 2/22. This conduit has proved a satisfactory method to establish right ventricular-pulmonary artery continuity.

Bioprosthesis↗
PubMed1979

Surgical management of an aneurysm of the left main coronary artery.

A 28-year-old woman underwent cardiac catheterization three months after sustaining an acute anterolateral myocardial infarct. An aneurysm of the left main coronary artery was found at angiography and also was visualized by two-dimensional echocardiography. The patient had no evidence of atherosclerotic vascular disease. At operation, vein grafts were placed to bypass the aneurysm and the orifice of the left coronary artery was oversewn to exclude the aneurysm from the coronary circulation.

Adult↗
PubMed1979

Papillary tumor of the heart: incidental finding at surgery.

A large papillary endocardial "tumor" of the heart was resected during surgery for closure of an interventricular septal defect in an adult. The theories of pathogenesis of papillary "tumors" of the heart are briefly reviewed. To our knowledge, this is the first report of a papillary tumor resected at surgery.

Heart Neoplasms↗
PubMed1979

PEEP and CPAP following open-heart surgery in infants and children.

The cardiorespiratory effects of 5 cm H2O end-expiratory pressure were studied in 22 infants and children an hour after open-heart surgery during mechanical ventilation with positive end-expiratory pressure (PEEP) and prior to endotracheal extubation approximately 15 hours later during spontaneous breathing (CPAP). Thermodilution cardiac output determinations and respiratory airflow, volume and pressure recordings were made to assess the effects of airway pressure changes on the respiratory waveform and oxygen delivery. Neither PEEP nor CPAP had a significant effect on cardiac output, intrapulmonary shunting, oxygen consumption, or oxygen utilization. Patients who had had pulmonary hypertension preoperatively did not behave differently from those without pulmonary hypertension when removed from ventilatory supprot. Expiratory airflow was significantly prolonged when positive end-expiratory pressure existed during both controlled and spontaneous respiration. During CPAP, this "expiratory braking" was associated with an increase in tidal volume and decreases in respiratory rate and minute volume. Because of the lack of improvement in cardiopulmonary function in this group of patients, and the possibility of untoward effects from sustained end-expiratory pressure, PEEP and CPAP might properly be reserved as temporary supportive techniques should respiratory function be compromised.

Cardiac Output↗