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Biomedical subjects

R B Allen

Publications and source records attributed to R B Allen.

10 recordsLinked to original sources
PubMed1996

Aortic root replacement with the pulmonary autograft in children with complex left heart obstruction.

BACKGROUND: The optimal surgical treatment of complex (multiple level or recurrent) left ventricular outflow tract obstruction (LVOTO) in infancy is controversial. Staged procedures expose the children to the need for reoperation, and currently available techniques of aortoventriculoplasty are associated with the morbidities of biological and mechanical prostheses. METHODS: Between July 1992 and January 1996, we have performed 24 aortic root replacements with the pulmonary autograft in pediatric patients (< 18 years). Of this group, 8 were infants and children with complex LVOTO aged 9 days to 22 months (mean, 8.6 +/- 8 months) and weighing 3.3 to 10.2 kg (mean, 6.3 +/- 2.6 kg). The diagnoses were interrupted aortic arch/ventricular septal defect/subaortic stenosis in 3, recurrent aortic stenosis in 2, aortic stenosis and subaortic stenosis in 1, and aortic stenosis/subaortic stenosis/mitral stenosis/regurgitation in 2. All patients had undergone one to three previous operative procedures (mean, 1.5 +/- 0.8 procedures/patient). Preoperative echocardiographic peak LVOT gradient was 71.7 +/- 25 mm Hg (range, 40 to 110 mm Hg) and aortic annulus size was 7.2 +/- 2.3 mm (range, 4 to 10.6 mm). The surgical technique included replacement of the aortic root with the pulmonary autograft combined with incision of the conal septum to relieve subaortic stenosis or accommodate for size discrepancy between the aortic and pulmonary autograft root and a pulmonary homograft placed in the right ventricular outflow tract. RESULTS: There were no perioperative or late deaths at follow-up (range, 2 to 25 months; mean, 13.5 +/- 8 months). Mean hospital stay was 15 +/- 17 days (range, 4 to 53 days). Three children had the following complications: diaphragmatic paresis (1), delayed pericardial effusion (1), and atrioventricular block requiring a pacemaker (1). In follow-up, echocardiographic findings showed absent aortic regurgitation in 3 and trivial aortic regurgitation in 5, and no significant LVOTO (mean peak gradient, 6.2 +/- 7.6 mm Hg; range, 0 to 16 mm Hg). Pulmonary homograft regurgitation was absent in 5, trivial in 2, and moderate in 1. Peak right ventricular outflow tract gradient by echocardiogram was trivial in 7, and a significant gradient of 55 mm Hg has developed in 1 infant. There were no infective or embolic complications during follow-up. CONCLUSIONS: Our experience shows that aortic root replacement with the pulmonary autograft can be performed in children with excellent clinical results. The technique of root replacement combined with ventriculoplasty allows definitive and simultaneous relief of complex and multiple-level obstructive lesions. Considering the growth potential of the pulmonary autograft, this should be regarded as the optimal treatment modality in infants with complex LVOTO:

Aorta, Thoracic↗
PubMed1988

Rapid decreases in phosphatidylinositol in isolated luteal plasma membranes after stimulation by luteinizing hormone.

Phospholipid concentrations were determined in plasma membrane preparations from porcine corpora lutea after incubation for 15 to 120 s without or with 0.5 microgram/ml luteinizing hormone (LH) or 2 microM dibutyryl cyclic adenosine 3',5'-monophosphate (dbcAMP). Treatment with LH caused a dramatic loss of 9 nmol in plasma membrane phosphatidylinositol (PI)/mg protein after 15 s of incubation, but no significant changes in other measurable phospholipids. Also, phospholipid concentrations were unchanged in untreated and dbcAMP-treated plasma membranes. The nature of the LH-induced decrease in PI was studied by incubating plasma membrane preparations for 15 s with [gamma 32P] adenosine 3',5'-triphosphate (ATP). 32P was incorporated only into three phospholipids: phosphatidic acid, phosphatidylinositol 4'-phosphate (PIP), and phosphatidylinositol 4',5'-bisphosphate (PIP2). Although LH generated small but significant increases in labeling of PIP and PIP2, less than 0.5 nmol of total phospholipids/mg protein were radiolabeled in 15 s. Phosphatidylinositol kinase activity, the enzyme that converts PI into PIP, was not affected by LH or dbcAMP treatment. However, incubation of luteal plasma membranes for 15 s with LH resulted in an increase of approximately 2 nmol 1,2-diacylglycerol/mg protein more than that observed in untreated or dbcAMP-treated plasma membranes. In summary, these experiments suggest that LH may stimulate hydrolysis of PI (and possibly PIP and PIP2) in isolated luteal plasma membranes.

Animals↗
PubMed1983

Dietary supplementation with vitamin C delays the onset of fatigue in isolated striated muscle of rats.

The purpose of this study was to assay the effect of prolonged vitamin C supplementation on contraction time and strength in the gastrocnemius muscle of the rat. Fifteen male Sprague-Dawley rats were given 30 mg of vitamin C orally per day for thirty days, while an additional fifteen animals served as controls. Contraction of the isolated gastrocnemius muscle was induced by electrical stimulation, and strength and time to fatigue was measured. Results indicate that the supplementation of vitamin C prolongs contraction time by 19% thus delaying fatigue but had no affect on muscle strength.

Animals↗
PubMed1979

Bowen's disease of the plantar arch.

Bowen's disease has previously been associated with the development of other malignancies particularly in patients with a history of arsenic exposure. A review of the literature is combined with a discussion of current theories regarding arsenic exposure, lesion differentiation, and prognostic implications. This report of a bowenoid lesion of the plantar arch emphasizes the importance of close follow-up of patients with Bowen's disease, especially on unexposed surfaces.

Arsenic↗